I've considered using QR, but he also has to have the durability for it. Something like +Def + Fury gets him to life 40 Def, I think. It works a lot like Lukas' usual built, albeit this dude can tank both ends (magic & physical attacks). You could also mix in a Delflect in there for SS, considering he'll get doubled no matter what.
If I get a Jakob, I want to give him a Brave Bow. Basically, a ranged Effie.
For a Slaying Bow build, Quick Riposte let's him make follow-up attacks and he has the natural bulk to take on most abuse that aren't lethal to him. So yes, go with that.
To further increase his bulk, he would like to be surrounded by Armored allies with Ward Armor and either Close or Distant Def seal. If choosing to go with Close Def seal, he may run Close Counter. If not, he can go with double Distant Def or Fierce Stance and a single Distant Def.
Just remember, Monster Jakob is fairly flexible to build as long as he has Speed bane or neutral. In fact, he can still run a Brave Bow build if you wish.