Father Prone to Verbally Attack - What should I do to level his moods?

I'm caring for my stroke/heart patient disabled father in his home after my mom passed away suddenly a few months ago.
He has a good deal of ability/mobility but he does have brain damage that seems worse some days than others. He has for the size of his stroke very good mobility but there are slight impairments. He does drive, what scares me with that is I have seen him on an off day and there are just days he does not need to drive and days he does ok. My biggest challenge is his complete resistance to certain aspects of my involvement. He doesn't mind "help" to a degree my mother waited on him hand and foot. He doesn't want my help with managing money, bills, prescriptions insist on driving everywhere vs. using the phone. I worry about some of the places he drives and the areas but if I try to talk to him about something like that he immediately just starts yelling that he is not going to be bossed around. I worry about the fact that he is a prime target for a mugging or similar and he just doesn't accept that. Also, the minute he loses something, forgets something, or has any kind of problem whatsoever, it is totally my fault EVERY time no matter how ridiculous. The last several days, he has become very very verbally abusive. While I live with him, he does not require 24/7 care thank goodness. I have a fairly demanding full-time job, but they are flexible. If I am not home when he wants/needs something he will hurt his back doing it himself and carry on the rest of the evening about his back. EVERY time it's something that could have waited a few hours. He is giving me an extremely hard time about work, which I am mid-managment salaried professional position. I don't work 8-5 and sometimes I have to work a weekend here and there. BUT, if there is something urgent I can have flexibility and be there right away. Right now, he constantly finds a reason to be angry because of something he wants or needs done while I am gone. I really need to keep my job, I'm single this is a good job with a good career path and he doesn't need 24/7 care right now which is a good thing. I guess I'm concerned about the lack of real authority or ability to make some important decisions if it comes down to it. And, I know I cannot stress wise handle a home environment where there is yelling and verbal abuse constantly, I just can't. But I am the only one that can. I am wondering if his Dr. is a good place to start with the extreme belligerance, I wonder if he needs some type of medicine to level his moods?