Need help building a fire damage strength-based Paladin.

For some context; this is a modded playthrough on PS5. I'm using Fade's beautiful mods, more enemies and encounters, and wings mod. Basically I'm making a half-cambion who's whole damage source is fire. I even plan to maybe use permanent Flame Blade as my main weapon, even though it might be pretty bad.

Anyway!

So I'm struggling to find the proper multiclass build here that would make this build shine. I'm thinking Searing Smite but I find it very hard to make Searing Smite worth it. I'm already smiting with Divine Smite, and at the cost of ANOTHER spell slot AND my bonus action, I get to deal a little tiny bit more fire damage. Worst of all, Searing Smite has a CON saving throw... which if I'm following here, would use my Charisma for its DC. Blegh.

So yeah, I need a bit of help. Thanks!