Can you run a vent in a right angle under the slab?

This is in the basement. I am trying to avoid messing up with the toilet drain plumbing as I am not sure how good I am with the plumbing and this is the bottom of the stack. This is the reason why below I am trying to reuse the bottom end of the grey pipe (the horizontal)

I want to relocate the vertical grey pipe (6) which apparently is a vent for the toilet (3) I am not sure if the toilet in that position needs a vent by its own. The grey pipe used to be drain for a sink that is not there anymore

The toilet drain connects to the bottom of the soil stack or maybe slightly above it and it is under 2ft away from it)

pipe 6 can move to position 4 (green pipe) or position 5 (orange pipe). They are all 1.5" (OD) copper
the soil stack is 3" copper

As far as I can see I have two options:
-(1)cut the grey pipe near the toilet drain and use a 90 elbow to reach 5 or used a 45 to reach 4
-(2)cut the grey pipe near where it enters the slab and connect using whatever fittings I need connect to the shower drain (wet vent?)

PS: For those following my saga (there is previous posts on this), I learned about these details this evening