Actually, when I look at those other two clues again, light dawned :-) 45a is defined by the first word that needs fixing, and it’s a two-letter sailor inside a biology term I did not previously know. 33d is also defined by the first word that needs fixing, and the next two words give an abbreviation that needs upending while the last three supply the last two letters.
btw, I found this endgame very neat, and although the thematic material wasn’t known to me a quick google provided everything I needed. I couldn’t resist getting my crayons out for an even more colourful grid than they actually ask for, cos why not!