Feels like there isn't enough time in the day to keep up w/ two households worth of errands, appointments, daily stuff. Any advice?

I would suggest that you look into some kind of private caregiving company or a federaly funded program called Senior Companion to give you a break on driving to appointments and being on hand to simply help out.
The private caregiving companies charge an hourly fee and can help when you are too stressed. Don't think about the cost of the service, instead think about the time you will have to do want you want to do. If you get sick from the stress of caregiving, the cost of your care will be much, much more since the family depends upon you for so much. I would also ask some of the families members to assist also and give you some extra time.

Senior Companions is a federal program in many communities throughout the US--contact your local Area Agency on Aging to find the nearest site to you. If there is one, call and make arrangements to enroll your mother into the program. Companions can drive her to the doctor's office for an appointment or wait until she is completed her therapy. If not located in your area, then still call the Area Agency on Aging to see what other kinds of services are available to you--many of there are free.

Get some addtional help so that you can minimize your stress levels and take time for your family--asking for help is not a sign of weakness, but a sign of a person who values her family and time for herself--

Contact a reputable agency that can provide companionship and transportation, help with meals, etc to give you a break. Sounds like you are at brink. Also consider hiring a local teenager or college student or stay at home mom to transport kids to activities for a small weekly fee. Many are willing to do so and this can save tremendous time for you while giving them the extra gas money and spending money they are seeking. A win-win.

On MILs Heath and pain mgt, consider asking drs to combine drug therapy with mandatory PT. This can really help. I'm an advocate for pain meds, muscle and inflammatory drugs but not long term with elders without mandatory PT or exercise program. My mom is 90 and was on multiple drugs and she seemed to get worsening dementia....we reviewed annually with drs but they kept renewing prescriptions and adding more for every complaint... My leg hurts, I can't sleep, I'm sad...on and on. Well a crisis occurred and mom got crazy and refused to take any drugs, period. I wasn't supportive of that, but wasn't able to monitor her everyday. She quit the drugs and it's been 9 months and she is better and emotionally better than the last 2 yrs. I don't advocate, but am convinced that all the drugs cumulatively were indeed not benefitting her.

It is a tough conversation to have. I don't know how old she is but in-home help is for anyone at any age as long as she qualifies and I'm sure she would. If you go that route you find an agency you like, call them, and they'll send out an RN for an assessment of your MIL's needs.

With my dad the "Help me help you" approach always worked. "I'm trying so hard to do what's best for you. I want you to be happy and to feel ok but I don't think just my help is enough. I think we need more help." Or something like that. When I would point out to my dad exactly how much I did for him and I worded it right so it didn't sound like I was complaining he was more open-minded to suggestions.

When our parents (or in-laws in your case) become elderly and need assistance there are a lot of tough conversations that need to be had. Does your husband pitch in with his mom?

There are some little things you can do to make things easier. I am in the same boat as you, and it seems that there is always one more thing to do. Something that helps a lot is to use a pharmacy that delivers. It's nice to have the doctors just phone them a prescription (or us call for a refill) and have it delivered to our door. I also schedule things together, e.g. trips to the grocery store and post office, so I don't feel that I'm coming and going all day. It's also nice to couple doctor appointments with outings, such as going out to eat. That will give you and your MIL a chance to get out in public some, which can be refreshing.

I notice you have some family members. You are so lucky, because you can delegate the chores. They are probably a huge help. It is so refreshing to have men on the group. It lets us know that women are not all alone struggling through this.

Wow, MCHM, the fact that your MIL is not yet 60 certainly accounts for her resistance to your efforts. I agree with Eyerishlass that you need to have home health care assessment done. The doctor can give a script for that and then you call one of the HHC agencies to send out a Nurse for the assessment. Not only will you get a better picture of her health care needs and recommendations, but the Nurse can also arrange for Social Services to come out and familiarize you with various programs and benefits available to your MIL as a disabled person. At least then you will have a 'menu' of options and be able to put some plan into action to relieve yourself and benefit your MIL.
As far as the meds are concerned, I would speak to the pharmacist and get all her refills aligned to the same date either monthly or every other month. I would also arrange for home delivery to eliminate many of those trips.

Does your MIL have dementia? Is she ambulatory? What are her needs?

Mandatory PT... they can do that & have it covered by insurance?

@Sue... We've looked into bringing someone into the fold to help out, but we're experiencing a lot of push back. She doesn't feel as though she's "old enough" for that to be an option. When she's lucid, it's hard to get her to commit to receiving any sort of additional help... she's holding on to the idea that with the "right combination of meds" she'll bounce right back; tough conversation to have.

@Everishlass... I am the husband lol! It's my wife's mom that we're trying to provide care for. She's not quite 60 so there is this desperate fight to cling to independence, to finding the magic pill that will allow her to drive, walk, travel on her own.

We're going to have a little discussion about timing & scheduling... it's one of those things that none of us really had any idea how this was going to play out. I mean, we can agree that an effort is made to be amicable while playing in the same sandbox but someone is bound to start kicking sand. There are some hot keys that get touched... now everyone is all lit up about how this Obamacare is going to shake out & impact her coverage... so in order to have an intelligent conversation about it, can anyone share some links or something that spells it out in plain English; talk about confusing!!!

Most of her health issues came to light while she was working so she is still technically on disability so the benefits are through a large national company but the fear is... with everything going on... how these healthcare changes are going to impact her? She's scheduled to have a couple more procedures by the end of the year, not sure if any of this stuff is going to be covered moving forward?????