Star Citizen can be used with VR, but it's using 3rd party screwing around type work arounds, and it doesn't work that well from what I've read. There is no in game support for VR. Chris Roberts said last year that eventually SC will have VR support, but as of now, not yet.
This is the projector we went with, mainly because it was a good deal @ $2k CAD open box from our local dealer we use for this sort of thing. I'm not an expert on TV/s etc, not even an amateur, but this unit was a big step up from our 1080p which was similar to the one you have now, but only 3000 lumens IIRC.
Our screen is smaller than yours, 120" vs 150", and typically a larger screen sees more benefit from moving up in resolution (ie a 24" 4k monitor is useless for 4k IMO, and 27" is just barely at the point where it's worth it, etc etc). Going from 1080p to 4k using the Disney+ and Netflix 4k streaming with say for example the Marvel films, is absolutely noticeable, very noticeable and improved in fact. It's 2500 lumens.
So far as the light in your room, I'm not the one to ask, someone else here might know though. Our projector room is in a room without windows, so I've not had to consider or notice this, but I know it can be an issue for any projector or screen. No real noticeable difference in brightness or ability to see the screen with our new 4k projector @ 2500 lumens vs the old one @3000, but again, it's isolated from outside light sources due to being underground/basement.
Overall it's been absolutely worth the switch, less than $1500 USD all in to upgrade and that doesn't count any $ I might get from trading or selling the old projector, which is still worth a few hundred at least at a minimum.