1. Is it likely that strings with a light coating of rust will break when tuning, if the piano hasn't been tuned for about 2 years?
Likely? No. Possible? Yes. Many technicians will lower the pitch of the string before raising it to minimize this risk. Some will even lubricate the termination points.
And I guess on top of that, will a piano that hasn't been tuned for more than 2 years need more than 1 tuning?
It will likely require a pitch raise, followed by a fine tuning; this should be done in the same appointment. Then, the piano will ideally
be tuned again in three months.
2. What do bent/crooked bridge pins mean? A piano I looked at a few days ago had the bridge pins bent on the highest and lowest notes. I hadn't seen that before and I don't know what the purpose of that is. It's also the same piano from the above question, if these two things may be related.
We would need to see pictures. Bridge pin holes are drilled on an angle, so it's possible that there is nothing wrong. Or, the holes could have been drilled wrong at the factory and then bent by the installer to hide the mistake. Cracks in the bridge could also cause pins to be out of alignment.