Fist of all, you'll get a lvl 4 trainer with about 15k salary for like 1000$. So don't worry about it. Using a lvl 3 trainer so far doesn't make such a huge difference as you probably imagine.
What are you training? Only one pop sounds a little few to me too, and it can have several reasons:
- you changed training every week
- you did not do one-position-training
the player had very low sub-skills
When looking at the players salary and potential (and age) I tell you: don't sell him. He's a great trainee and could make a great SF one day (if you can be patient). Just stick with training one skill after another and you will see great progress.
PS: No, he is not screwed, even if he received a little less training. Just imagine he gets injured for 2 weeks. That would be bad, but now reason to dump him.