I've decided I'm going to make my boyfriend suffer by destroying his self-esteem before dumping him so he falls into a depression.
That sounds like a terrible thing to do.  What makes you want to do things like that to people?
I need time to take care of myself
No one deserves to have their mental illness be taken advantage of. You need supposed to be supportive of him, or if you can't do that, at least don't try to push him deeper into depression. This could cause him real problems.
I don't want to be a burden on him and it's not even my fault since he has a low self-esteem. I want to make sure that he rots in depression without me.
It is very concerning that you feel that he deserves to rot in depression, and you sound as though you have some anger issues of your own. Instead of maliciously sabotaging him and yourself as well, you should consider going to a mental health specialist. It would probably be good for both you and your boyfriend to go to therapy.