Hard to say. Five dates in two months isn’t great, but it isn’t awful, either, particularly for someone who has so many other things going on in his life. That’s a date every 12 days or so. I like that he keeps in touch with you on the days that you don’t see him.
Still, I’m curious what he’s doing on the weekends he doesn’t see you. I went to grad school but I didn’t usually study on weekend nights. Are his baseball games on weekends? Does he invite you to them? Are you two exclusive? Is there a chance he’s dating other women?
I don’t know your guidelines for “serious” dating, but clearly he is showing interest in you. The real question here is whether or not he’s showing enough interest for your liking. He could be giving you as much time as he possibly can and it still may not be enough for you. I think the issue is more about compatibility than seriousness.
Thanks for the question.