That yellow pre shot is good. The next one is virtually the same number once meter variance is factored in. Let's see how the rest of today plays out at this dose. If he stays flat in yellow all day it can be a sign that his numbers are about to drop. This isn't a rule, merely an observation that many people make.
Yes, that's a good thing. A day of flat yellow numbers should be a heads up that there might be some BG lowering action. It might not happen though. If he's still yellow at PMPS give the same dose and test at +2 this evening for sure. That +2 test can often give advance warning of a drop to come. If it's significantly lower than PMPS, be prepared to monitor more this evening.
If the number is higher than PMPS at +2 it generally means an uneventful or even a bounce (higher numbers) cycle. If the +2 is the same or lower than PMPS it can mean that he'll drop lower than he has been doing. If +2 is significantly lower than PMPS (100 points or more) you can try slowing the drop by giving a small snack of his regular low carb food. This situation warrants more tests in case he drops to green numbers by nadir.