1) Ask nVidia support how big the PS should be for the card you have.
2) Buy a 500G SSD as the primary drive and move the 2TB to secondary data drive.
3) Ask Dell about upgrading the PS for your current case/model; otherwise, ask Dell about a possible trade-up to a larger case with more slots, more in the PS.
4) 16 GB RAM should be fine.
5) Sorry for this Laz, but as a gamer, I am a bit surprised you didn’t seriously check out the unit before you bought it. :-)
I suck.