1. Stamina refers to how much a pitcher can pitch. A pitcher with 70 stamina might be able to go 6+ innings every outing, but another pitcher who only has 20 stamina might only go one inning. Therefore, when choosing who to start and who to use in the bullpen, stamina should be an important factor, but not necessarily the deciding one. Usually I try to make sure my starters have stamina of 60+, but if they have dynamite stuff and only 50 stamina (see
Al Serra) then they could conceivably still be starters. Long Relief guys usually need to have 45+, but they are weaker than your starters. Everyone else I use as Setup A or B, since I don't use a closer.
2. Durability refers to how soon a pitcher can pitch again after an outing. In real life, some pitchers (relievers mostly) can pitch every other day, like RL closers. Well, in here, some pitchers can do this too. Starters usually have anywhere from 15-40 durability, meaning they can pitch every 3rd-6th day or so. IF you can find a good starter with 30+ durability, you are in business. Relievers can have anywhere from starter durability to 80 or even 90 durability (these guys usually have low stamina, so they pitch about an inning an outing, but they might can do that for 3 days straight, have one off day, then do it again.) So durability is important in pitchers.
Durability also refers to how soon a position player needs a rest. If they have 70 durability, they might only can play 120 games, but a guy with 95 durability can play 150 or 155.
3. This is generally correct, except for a few categories. For batters, this means the push/pull rating. A low rating means an extreme pull hitter, but a higher rating means extreme push hitter. Someone with a 50 rating will hit it both ways about the same, but someone with a 100 will hit it almost exclusively to the opposite field.
For pitchers, there is the FB/GB tendency. This is tricky, because a higher rating is viewed as better, but it doesn't have to be. If a pitcher has a low GB/FB rate, he will pitch more flyballs, and a high rating means more ground balls. If he has a higher rating, in theory, this will lead to a higher rate of double plays and the like, with less sacrifice flies. But you can find a pitcher who can do it well with low GB/FBs. While
Gorkys Romero uses his high rating to his advantage, you can find dynamite pitchers like
Wilfredo Garrido, who can still be electric with a low rating. Hope this helped.