Thursday July 4 2024 Content Updates says that “painful” was added to the allowlist for the 苦 kanji last year, so that shouldn’t be a problem any more I hope.
More generally, kanji meanings aren’t super important or tightly defined compared to word meanings, so while you probably want to try searching the forums or asking if there’s a reason not to accept the answer you keep giving for a kanji item, to check that it’s not too far off the central idea for the kanji, I think it’s fine to be quite liberal with defining synonyms here.
For mixups of two readings or meanings, I sometimes have luck with working out my own little mnemonic specifically for distinguishing which way round they go; then as long as I pause a bit before answering I can think through the mnemonic. Eventually also repetition will help here.