Dealing compassionately with harassment

[MavisDavis99]

I know, odd title, not sure how to explain....
Split with baby's dad when 6 months pregnant, 3 years ago.
He has never contributed financially and seen his child only a handful of times.
Asks for phone contact with him but doesn't call at agreed time/day.
Does, however, try and call me at other times and text me on a daily basis, despite being asked not to. I've blocked his number (though annoyingly my phone still notifies me every time he tries to call and shows his texts)
Also emails me asking to speak to me and saying how much he loves and misses me.
Despite telling him he's blocked and to stop, he doesn't. Ignoring every message for 6 months hasn't stopped the daily stream.
Really wanted to do "right thing" and leave the door open for contact between him and our son, but the stress is too much for me.
I know he's struggling mentally and has made suicide attempts, so I want to deal with this compassionately, but I am at the point of just changing my number and blocking email and taking the opportunity for a father son relationship away because it's just too stressful being on the receiving end of his messages/calls/emotional declarations. Any advice?

Stop trying to caretake him and block him. What kind of relationship do you think he is going to have with your son if he can't be reliable and he's still fixated on you?

Thanks. You're right. I try and be understanding, but it makes no difference.
Part of it is I guess selfish as I don't want my child to grow up in the likely knowledge that his dad killed himself, but equally, he's failing him already, so unlikely to ever be a halfway decent father.
He's blocked on my phone but it still notifies me, so getting multiple messages a day that x has tried to call and been blocked still feels like harassment.
Guess I need a new number.