He doesn't have to just hand it over. He can throw it with the intention of taking off MC's head but that wouldn't still stop MC from being able to catch it. Steve's only fault in having a shield caught is throwing it in the first place and that's it. In scenario 2 there's not much he can do trick wise since it's an open field. May not be enough room in the first scenario depending on how crowded it is. I don't know the durability of Halo guns but if it's not anything spectacular then it gets destroyed when Steve tries to disarm him unless he aims for the wrist.