I live in an old house and I have noticed that smells play a role in their charm. Will, not really charm. But they can stink. Any vinegar based cleaners that you can make at home should help neutralizing the odor. Vinegar is great for strong odors. Stinks when you're using it, but dissipates to neutral pretty quickly.
I've found several recipes online that I now use everyday.
What I learned was that paint on walls/ceiling and the floors are the biggest retainer of odors. Assuming you don't want to rip your carpet out and clean the subfloor, you could try to wash the walls and ceiling with a detergent. Washing the surface as best as you can without damaging the plaster might help get rid of the smells.
The more thorough the better.
Once dried, prime with a good odor removing/covering primer. Look for products that are aimed at houses that had smokers or un-neutered pets. Then paint. I would strongly recommend hiring a good house painter for this. They probably know of good products and can get the painting done very fast.
Lots of fresh air is fine, but will have limited success. Over the decades a house gets lots of oils and other residues on every surface. It is not easy to get rid of those things.
Clean and cover or replace.