About the mnemonic and memorization, I put my recommendation in another post.
Try to make homophone-based mnemonics based on another Japanese word. Try to break down vocabularies into imagined origins (even if it is a false etymology).
It depends on your experience or previous memorization, so possibly
- はん is probably 半 (half)
- けん is sword, as in 剣道
Confusions would be more apparent in higher levels. Try KaniWani, and you will see even more confusions.
Anime Context Sentence is good, but I think you need more than that - various groups of meanings, and sentence / phrase synthesis.
I also mentioned Goo JE in that post, but another thing would probably help is, Context > Pattern of Use.
I think I used to use Item Marker, but I don’t know what it is like now. ConfusionGuesser would probably be nice too.
In any case, try to learn more than merely SRS system allows.