It sounds like you're both kind of vacillating. This is pretty normal. There are obviously reasons you guys broke up or you wouldn't have broken up. But there are also reasons you were together in the first place. So y'all have mixed feelings. You want to be in touch because you like each other on some level but also on some level you probably both recognise that it won't work and you need to move on.
If I were in your shoes I would block him, properly go no-contact, and move on entirely. It seems harsh but IMO it ultimately would be the kindest thing to do for both of you.