Regarding bench pressing, how many reps would classify the weight as too light-10 reps? 12 reps? 8?

Depends on your goals. Generally, we have three ranges for weight training depending on goals.

1. strength training. What athletes do. Heavy weights, low repetitions. Under 5.

2. General conditioning. For general strength, health, bone health, fitness. 10-12 reps, working up to 15 before adding weight and going back to 10.

3. Bodybuilding. Muscular hypertrophy. 12-15 repetitions and multiple sets, often 5 or more. Coupled with special dietary strategies.