Clutch, tire bumps, and recommended tire size

Hi everyone, I've got a few fairly simple questions:

1. CLUTCH: After lending my car to a friend for a couple weeks, I found my clutch was slipping - engine revving while accelerating with foot off clutch, and the clutch releasing near the top of its range. I've been driving the car myself, pretty slowly and releasing the clutch slowly, such that the problem is not exacerbated. Now it seems that the problem has gone away. Is it possible that the clutch can be "trained" back to its working state? Also in the past my clutch pedal squeaks while being depressed. It went away now, but is this a problem?

1. TIRE BUMPS: There are weird, irregular bumps along the side of my tire. They are a bit discolored too. It seems that this might have occurred after a 500 mile trip, a few stops. I have goodyear integrity's, speed rating 92S, i think? Is this a problem? It has not been a problem for me yet, i rotated my tires yesterday.

2. TIRE SIZES: I have a friend with a nissan altima with OEM tire size

Thanks for all your help in advance.