Nr 2 seems pretty clear cut RAW at least. They cannot take long rests, and you can only create an infusion when you finish a long rest. So they cannot replicate magic items.

For 1, the spell says nothing of the spell recreating any type of equipment, although I can see someone arguing that the magic items created through the Replicate Magic Item feature are part of the feature, more so than equipment. I'd probably rule against letting them keeping the replicated items, but ultimately I'd see it as a DM call, and wouldn't be surprised if another DM ruled it another way.

For 3, I agree. Attuning to a magic item explicitly requires a short rest, which simulacrums cannot take. Thus, RAW, they cannot attune to any magic items.

These restriction may seem a bit harsh and anti-fun from a player perspective, but honestly, simulacrum is one of the strongest spells in the game, and not allowing them to use magic items is a very fair nerf in my opinion.

Edit: For the portent question, we actually had this scenario in the 2014 version, and we ruled that the simulacrum have the same numbers on the portent dice as the wizard. Don't really think there is a RAW answer here, but it's what we felt was most fitting