Like your pronunciation changes in context? Or something else?

I think I say both forms of "hoodlum" depending on who knows what - I don't use the word that much. Also, I use both "grade 9" and "9th grade," both "on accident" and "by accident," and I usually say "Mom" but sometimes "Mum," both spelled "Mom," but I recognize "Mum" as acceptable spelling. And it's not on the list, but I have a hard time spelling "labor" and "harbor" instead of "labour" and "harbour," but I don't spell "color" "colour" for some reason. Crayola crayons, maybe?

I use both Xth Grade and Grade X depending on who I'm talking to -- with Americans I tend to "correct" to their construction of Xth Grade but among Canadians I definitely say Grade X, and Grade X is what I consider to be the natural form for me. "On accident" sounds completely whacky to my lexicon, but I noticed sometime in high school that some of my American friends said it. I think it's interesting that your lexicon seem to be a mix of what I consider American English and Canadian English, though those are generalizing terms more than anything.

There's nothing on here about spelling because it isn't something I deal with much in linguistics, since it isn't a very good reflection of spoken language and is basically arbitrary. TBH, I don't even know what standard Canadian English spelling is for many words, since it's a hybrid and doesn't seem to follow any particular pattern as to whether or not it follows American or British standards. When in doubt I go with British spelling, though.

Wait, I wrote all that and then realized I did ask about the spelling of mom. In that instance I asked because I get the sense that here in Canada it's a bit whacky -- I have always assumed it was mom, pronounced as spelled, but Frances uses "mum", and I think my friends say "mum" when addressing their mother and "mom" when talking about a generic mom, but they would all spell it with an O, I think. So there might be some weird shift going on there, it's curious.