Braindrop, you are doing awesome. Please don't beat yourself up over totally reasonable delays. Like going out with your girlfriend, and doing things with and for family. I agree with a lot of people here that moving to a "it's done when it's done" is a better model, but I understand that having specific due dates helps motivate you, and that is fine. But give yourself a lot of slack for missing due dates. None of your true fans, of which you have many, really mind at all as you can see from the comments here. If you are a week or two from your target, I'd say that is totally on time compared to most devs.
I like your idea of giving yourself a buffer, that should take some of the pressure off. Life is hard enough, without putting undue pressure on yourself, so I hope you can take some time to pat yourself on the back for a great game that brings enjoyment to a lot of people, and the fact that you can get some extra income from it, which is a huge bonus.