[JoshuaD]

First situation: Check every single time. Your hand is simply not good enough to take the lead here. Raising preflop destroys your postflop expectation and isn't very +EV in the first place. OOP with a low PP sucks, especially against more than one opponent. (It still sucks vs one).

Second situation: Call.

55: Ditto.

77: 77 is close. 99 I'm raising every time in these situations. 88 I'm raising like 2/3's of the time. 77 probably around 1/3 of the time.

Those aren't based on randomness. It depends on my opponents whether I raise or call. The more likely they are to c/f the flop the more likely I am to raise.