Mature thing to do?

Me and my ex have a two year old together. We haven't been in a relationship in a little bit over a year, and he has a new girlfriend and they have a son together who is only a few days old. Me and him always had problems but it got way worse once we had our son. I grew up and matured and he wanted to stay the same old immature kid so we just didn't work out, not to mention things got abusive. I'm not going to lie I've held a grudge towards him for a loooong time. He has been in and out of our sons life. I've tried so many times to get him to be here and he would be for like a week or so and then go right back to his old ways. Then when he got that girl pregnant he just completely ditched our child and hasn't seen him in 4 months now. (Our son doesn't even know him like at all) I'm not going to lie, I did get salty and would send him smartass little texts about how he could just ditch our son because he has a new family now and honestly I was salty when he got with that girl too because he was leading me on acting like he had wanted to be with me when he was with her. So I'll admit I've done things wrong. I've decided that since he's no longer involved in our sons life I want it to stay that way. At least until my son is old enough to decide for himself if he wants to be around his Dad. So for now I'm just going to block him and his girlfriend off of everything and just move on with my life. But I did decide to be the bigger person in our situation and send this text (because he's said some shitty things to me as well.) and I was wondering if it was just the best thing for me to do? Like I really just want to move forward and get on with my life because I'm not going to lie I have been stuck on this whole things for a long time and now I feel it's times to finally let go. We're still teenagers, I'm getting my GED this year and then next I'll be starting college and getting a car. So I have very exciting things happening and I just want nothing but a positive life and I can't have that with him around because he's toxic. Here's the text I sent him. I just want to be the bigger person and apologize and own up to my part in being wrong and moving on. He on the other hand will never do that.