Honestly I would find it very strange if doevm couldn’t use his immense knowledge to temporarily mega boost his mana pool through some sort of ritual, the magic has to exist and if it exists the forbidden one has it
he's going to win in 3 spells 1 to remove mobility and disable spell components 1 to reduce visibility and the 3rd will be a simple fire spell to light the bag of gunpowder he has
smokescreen, throw things, more smoke, lightning spell, stabby stabby, run, fireball, repeat. simple but affective. oh and water to make lightining more affective at some point.