I really feel for you because I've been in this situations SO many times, and react the SAME way you do (freaking out and asking if they are done with me, etc). Honestly, it sounds like he just isn't that into you, or he is talking to other people. And he doesn't sound like that nice of a person either. I've kept my eye on people's snapchat scores before to see if they increase, and they always do. He has time to snap other people but not even 30 seconds to reply a text from you. I need to stress this, if he wanted to talk to you, he would. You definitely aren't a priority to him, and are just an option. I know he is busy, but blowing you off multiple times is shitty. You even try and accommodate to his schedule all the time, and just want to see him to drop things off and he's just not having it.

Him talking about sex a lot is kind of off-putting too. Like he talks about it but won't even make time to do at least that? Leave him behind girl, you seem sweet and you can probably do a lot better. You would be dodging a bullet. Get someone who is excited to see you/talk to you as you are talking to them. It will feel shitty but if you aren't too invested at this point, you will pick yourself back up soon. I don't think it's running away, it removing yourself from a situation that is just not for you.