Yes, we can cut off federation with other instances. We have already done so with a small number of bigoted instances. https://lemmy.blahaj.zone/instances. You can also find the link at the bottom of each, labelled "Instances"
And downvotes are disabled simply because I don't like them, and up until a week ago, I was pretty much the only active user on this instance :)
If people really want them back, I'm not completely against enabling them