Wye when horizontal, so it's good. Never San T in the horizontal plane; only San T when a drain goes from horizontal into a vented stack (vertical).
Vent where the old #1 connection is. I can't see that connection in the picture, btw. Vent the sink, as you described, going across the ceiling and down. This makes a vented stack for the sink so its drain needs a San T to connect to this vertical pipe.