Spd+ Def- Halloween Jakob Build will this work?

Problem with fury is how he takes 6 damage after combat. His Wary Fighter may slowly deteriorate, and even at a speed of 29, most units are still able to double him.

I suggest for his weapon (Opponent's phase) Guard Bow+ which grants him a distant counter 3 seal. And as for his A-slot; Earth Boost 3.

If you intend for him to become more of an attacker, go for the Death Blow 3 + Brave Bow build. Your H! Jakob should still perform well offensively.

Spd is most likely his worst stat, but even if you have a bane in Spd, the gap between different IV H! Jakob performances are not too far. He is still, indeed, a great unit to use.