As a foreign speaker, I find some of your examples curious, because for them it would actually make it harder for me to deal with English if we went with those suggestions. Reason being that some of these words reflect similar semantic changes in my language, and losing them would feel unnatural. "Who" vs "whom" is a good example.

"It's" vs "its" is also bothersome, but for a different reason - this probably has to do with learning English in a way that emphasized formal sentence structure, rather than just the way it sounds. But I think that's not all that uncommon for non-native speakers. When I studied in college in New Zealand, I once had a chance to converse with our ethics teacher (native Kiwi) one on one, where she remarked on my spelling in a recent essay. From there she quickly went on to a general rant about how immigrants are much better than natives at spelling, citing "its" vs "it's" as one of the examples - according to her, she had never seen a non-native speaker substitute one for the other inappropriately.

On the other hand, "if I were" never made any sense to me, and is one of the more common mistakes I still make, even after 8 years of speaking and writing English 99% of the time.