I've lived in homes with original trim similar to what you want and some of those doors were stuffed in corners like yours. They just cut the trim on the wall side to fit, as though the wall had eaten that side of it. It looked okay because it was obviously built like that and because it was old, it was allowed to be quaint. Is your home old enough for quaint?

If the squished doorways are in bedrooms and halls, but you have space to do the big trim in the "fancy" rooms, you could maybe do a simpler, smaller version in the private areas. I'd be consistent within rooms though.

In the tight fit doorways, you can use a 1X3 (2 1/2 actual) and steal a bit from the reveal (about 1/8") at the doorjamb so casing trim doesn't touch the wall. As long as the trim has the same configuration (flat) it may look okay to you and that's what's important.

The header will have to be reduced to about 4" to compliment the narrow casing trim.