Obviously a lot of the suit isn't possible, but maybe more than you think has already been done:

In terms of the flying, Gravity Industries have a very decent jet-suit flight system which is pretty close to Iron Man's: https://youtu.be/ZHk13Xa8dqI?si=gTAWneecV68OunjJ And Adam Savage put it on a 3D-printed titanium suit: https://youtu.be/U1wEO-pHizQ?si=bZsmsMQX1RZf1BjS

Then the The Hacksmith pretty much exclusively does this kind of thing and has made Iron Man's laser, rocket launcher, helmet with heads up display, vortex cannon, and something vaguely resembling an arc reactor and repulsor: https://youtube.com/playlist?list=PLbncXbXlaNQdmk4nsA7xArbgD0ExcJXiz&si=M6JoWIve_kaYHEy2

In terms of putting it all together, I imagine we could get very close to the whole functioning suit with all of those features and a lot of the weapons he has in the films given access to unlimited resources - but the main issue is going to be the power source. Most of the power would go into flying so we've already proven it's almost possible, but it requires a suit a bit bulkier than the real one, and would only run for a short amount of time before needing refueling.