What factors do you guys take into account when deciding on tempo? Generally I'll look at the other teams depth first, then defensive ability, defense they run, then other things like how many turnovers they force a game and their speed and athleticism ratings. 

If they're running a 7 or 8 man heavy rotation, I'm probably going up tempo. If they are just below average on defense I'll usually run up tempo there too, however what else should I be looking for in the other team or in the other team compared to my own team to help decide where I should be tempo wise. 

If I cut a senior who I played in like 7 total games last season while everyone else got 31, is it going to cause guys to transfer? He's one of six seniors and I would rather get another freshman this year and shrink that class a little but not at the expense of losing someone else. Is it completely random or if other players are getting solid minutes (10+ per/game) are they not going to care that that guy is gone?

For tempo, I believe, you need to be more concerned with your own depth chart. It used to be running uptempo would tire out the opposing team, but I think that has since been limited. If you're team is far more skilled than the other team, or your bench is far more skilled than your opposition than going uptempo might be a good idea. In general if you are facing a superior team you probably want to go slowdown in order to limit total possessions and give your team a better chance at the upset.

Also if your team is young you probably don't want to use uptempo because of the potential for foul trouble. I can generally think of lots of reasons to not go uptempo, but that may be a personal bias. I don't like running uptempo and have had wide varying results from my limited experiences.

How much more important is Speed, for a Point Guard, than Athleticism?

I have a Point Guard with about 55 athleticism and 65 Speed. Is it better to get the point guards who are less balanced and have closer to a 85 Speed with 25 Athleticism as their build? 

Also does speed affect Centers very much or is it better to just max out with as much athleticism as you can. For example, Is an 80 Ath, 15 Speed, Center going to perform better than a 60 Ath, 40 Speed Center?

In both cases, I would take the guys with higher athleticism, all else being equal, and assuming I am not running the FB.  Easy call.  Don't know enough about the FB, so I would defer to someone else on that.