I will train JR and JS for the rest of the season
Not JS, train OD, so JR and OD.
I'm not an expert on the salary estimation but if you consider that it will take 2 weeks to have 1 pop in OD and 2 weeks to have 1 pop in JR, you can more or less guess the level of those skills at the end of this season. You can then calculate the estimated salary at http://www.how8.com/bb/index.php. Now I don't think this is up to date but better than nothing right?
I would probably do 8 weeks of JR (that should give 3 pops in JR, 1 or 2 pops in JS, driving and handling depending on the sub levels) and the rest of the remaining weeks (6 weeks without counting the playoff, but if you want to train during the playoff too, then 9 weeks I believe) on OD. 6 weeks of OD should give 3 pops in OD (but could be 2), and if you're lucky you might get a pop in ID, handling and driving. If you do 9 weeks, then you should be able to get 4 pops in OD.
So at the end of this season, player A would look like
Jump Shot: proficient Jump Range: mediocre
Outside Def.: prominent Handling: mediocre
Driving: mediocre Passing: respectable
Inside Shot: proficient Inside Def.: proficient
Rebounding: respectable Shot Blocking: strong
Stamina: mediocre Free Throw: atrocious
and
player B would look like
Jump Shot: proficient Jump Range: strong/proficient
Outside Def.: proficient Handling: proficient
Driving: strong Passing: mediocre
Inside Shot: respectable Inside Def.: mediocre
Rebounding: mediocre Shot Blocking: awful
Stamina: inept Free Throw: respectable
This is not that accurate I belive (since I'm still not an expert) but you could expect to have these players like this.
And regarding the trainer lvl, I would say stick to lvl 4 trainer, it should be sufficient in div IV. To buy a lvl 5 trainer, you have to spend something like $400k or so which is pretty expensive.
I think the difference between lvl 4 and 6 is not very big. Again, I'm not an expert on this but I think it's only a difference of 2 to 3 weeks.