So, the turbine looks ok from what I can tell, clean and dry. The white shows it was running well, no oil. The broken bolt wont cause a leak but can cause other issues, especially if others back out. If the center section comes loose wheels will rub the housings and BOOM. The broken bolt and what looks to be a loose bolt makes me a little nervous but if all the other bolts are good and tight, you SHOULD be ok…. (Disclaimer here)
Just what I expected, the front of the comp wheel is filthy!!! That was all coming in the air-filter or the crankcase breather line before it was removed. Bad maintenance. IF you took the compressor wheel off the shaft and look at the back of it, it would look like the scudge on the backing plate, but DON'T TAKE IT OFF. The compressor blade edges look cleaned off just like the wheel contour of the housing. DO YOU THINK THEY TOUCHED THE HOUSING?
My recommendation would be to get a rag and some brake clean or some other solvent on it and clean everything in the compressor end; blades, housing, backing plate and all. Then spray out the hot pipe with the same. You can also dismount the intercooler and see how much oil there seems to be in there. If lots, clean it out. Then once cleaned, put it all back together, run it for a few hundred miles (with a new air-filter) and then pull the hot pipe to see if there is a bunch of oil in there. If it's only a fine film you should be ok because that's normal on an older turbo.
Before putting it back on the car, do the rock test. With the turbo completely assembled grab the nut on the compressor end and the nub on the turbine wheel with your thumb and index finger. Force them opposite ways radially and turn the rotor. Do this a few different directions. You're trying to make it rub the housings, if you can the turbo is junk, if not, run it. You can also try axially, pushing the rotor toward the each end and spin.
The only other option is to buy a new turbo and do all the same cleaning to the pipes and intercooler. Being a turbo guy, myself, I'd try it first and see where it gets you. I've been running well used SR20 S14 GT25BB with a large internal crack in the turbine housing for more than 40k miles and never had an issue.
Let us know what happens.