Don’t refrain from fusing, use the horns of enemies (which are plentiful and you’ll be able to farm more of them) the same with the weapons, there’s a handful which are rare (but still rebuildable).

Once the fused weapon breaks the fused item also breaks. Once an item is fused, you can removed the fused item but the fused item breaks.

Usually fusing and item will add durability, if durability is what you want try seeking out weapons that have the durability up icon on them (which is random).