I think that sublevels are taken into consideration on all calculations.
It's definitely the case in #5 on salary calculation. In fact, I'd guess that is one of the ways the very existence of sublevels was suggested (i.e., comparing the salaries of two players with the same integer skills).
As for 4, I actually would say that it can be somewhat important. There is a wide range of DMI that corresponds to an integer level of GS (other than 9 GS - that's always the same barring training increases or skill drops). If you know your player's max DMI, then you can get a sense of whether he is at a high sublevel or a low sublevel, and get a general sense of how well he will perform relative to his best play.