I am guessing the sliding drop out on the other side has the brake mount on it so the brake caliper moves with the wheel? (to answer the brake question above)
That is my preferred system of sliding drop out – none of these stupid slotted caliper mounts were you have to readjust the caliper using guess work.
Are you screwing directly into the aluminium drop out or did you use chainring style insert nuts in the back face we can’t see?
Not sure about the exposed snubber bearing but I guess it is easy to clean or replace and it’s not going to cause much of a problem if it gets sticky as it’s not actually touching is it?