1) Usually the nature of the lift chosen for light day makes it light relative to the main lifts done on the H and M days, but in this case using the BP that will not be the case. So, here you can train it heavy and restrict it by doing something like a 5x5. Weight can then be what you can do with good form for all those sets (Likely in the 80% of a heavy 5).
2) Yes, incline the day before PR as indicated here may give you issues.