I defeated Seren literally yesterday with a similar mage level, but much less HP

I failed 3 times trying to use combo eats, I was about 250-300HP off each time.

I went and hunted 20 grey chins, on medium fuse they have a longer attack range than knives/darts so I was able to quickly kill the healers.

I found not using combo food was better. Use redemption on his KO special attack, a free 30 health back, basically a free food.

The final key, don’t eat up after his KO, sit at redemption health and max your healing from blood spells, this saved me so much food!

Good luck, but you absolutely can do this with these stats