what i have to say is probably not what your going to want to hear and i am sorry for it. but the truth is you should break away from this person completely and move on with your life. i have been where you are with being broken up with over " wanting space". my situation was different in the fact that my guy did need space and he came back pretty quickly. i too was devastated and crying and depressed.
but your situation differs because in fact he's been gone for a year and half, and has even had another gf's in the process. he doesn't want to be with you, you don't block people and ignore them when you want them in your life.
it sounds like he is toying with you, he knows you want him back and can get an ego boost when he talks to you , then he can drop you without a second thought and not think anything of it since your not together. the fact its been happening for a over a year is concerning, at some point your going to have to realize he's not coming back and he's using you. you need to flip the switch instead of giving him the attention he wants, ignore and block him. remove him form your life completely. your better off without this guy.
i do get your feelings of sadness and that you want him but its been a too long. in my case it was only a month we weren't together. and he still told me everything he was doing and wanted to see me and know what i was doing. this is not the case for your guy. he's playing you and your letting him. again im sorry if this sounds harsh, but from what you described above he's being worse to you, and there's plenty of people in the world who im sure would love to get to know you. i hope you get feeling better