Using the commode. Is there a better solution for this?

Placing a bag in the basin of the commode and emptying it right away helps.
Placing a bit of water in the basin then emptying into the toilet will also help.
A commode in the room is not going to create any more odor than changing a soiled brief would.
Are you not able to get him into the bathroom? A wheelchair with a commode hole can be wheeled and placed over the toilet then the fan in the bathroom would take care of odors. If it is a matter of the door not opening wide enough there are "full swing hinges" that will allow the door to open more giving you about another 2 inches of space.
Placing a ceiling vent fan in a regular room might not be enough. Vent fans in bathrooms are rated for the size of the room. So if you are going to place a ceiling vent fan in a bedroom measure the square footage and get a fan that will do the job. You may have to get more than 1.
A window fan turned to allow air to go out of the room might work. You would close the window and remove the fan when it is not in use or make sure that the fan you get has a way to seal it off.

An exhaust fan will help air the room quickly. I use styrofoam around the fan in the winter (taped to the window and fan frame) and an inside complete cover in the winter months (when not in use). I have also built a "box" with a bathroom exhaust fan mounted in it to accomplish the same function. before these fans were available. Exhausting the air quickly removes the smell and because it is pulling air from the rest of the house, the room doesn't get cold.

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Vent the fan OUTSIDE. A lot of people have it blowing IN, to save the cost of heating the house...and you might as well quit if you're not setting the fan correctly.

We'll be putting a commode in mother's bedroom soon. Brother will add a fan to the drop ceiling that will vent outside.

I think the water in the commode with Poo-pourri is a great idea. That stuff really works!

You have to be quick on the draw with an incontinent elder. My grandbaby can stink up a whole house in minutes when he fills his diaper.

AND if you are cleaning an elder's diaper, for the love of heaven, bag up the 'messy ones' and get them out of the house, pronto. Mother has a 'diaper genie' adult sized and it DOES NOT WORK!!

When my husband was completely bedridden in our living room, he too had to use a bedside commode in the living room to poop in, and I too was concerned about stinking up the house. I always put about 6 inches or so of water in the commode and then sprayed the product Poo-Pourri in the water, as directed, and I never once had an issue with my house smelling like poop. That stuff works really well, and I always keep some of it in both my bathrooms for guests when they come in case they too don't want to stink up my bathrooms.
I buy mine at QVC, but you can buy it at Walmart, or Amazon as well I'm sure. Best wishes.

Bowls if vinegar help.

A bathroom ceiling fan can be installed above the toilet area to vent the room. And disinfectant spray is your friend