Actually, I don't think his last message was too bad either.
He sounds disappointed because he clearly felt a connection and, when you've done OLD for a while, you'll see that his communications, however, imperfect, are a damn sight better than most! 
As for this, Oh I forgot to add, shortly after his final message he deleted me on Bumble. I’m mean seriously, what would he of been like in a relationship, that is also completely normal. Why would you keep someone who had rejected you on there? I always deleted and blocked someone if I'd met them and hadn't wanted it to continue.
You say you tried to be honest, but not horrible, in your response, it sounds like he did the same.
FWIW, I also hid my profile quite soon after starting talking to someone I was interested in. I have no interest in 'multi dating'; or chatting to lots of people. I viewed OLD as similar to meeting someone in a pub or whatever - if I started talking to someone and found them interesting and wanted to see if it could go anywhere, I wouldn't continue to be open to talking to every potential male in the place on the off chance I might meet someone 'better'. It's fine, in those circumstances, to decide that you no longer want to continue the conversation - for any reason and after any duration, but I wouldn't expect them to still keep me on their radar!
I agree that photos of his kids was too soon but, if he is also new to OLD, then there are rules that he is also learning.
His response didn't suit you, but it was fine. Deleting you is normal.
He might well have found your requests and rejection for quite arbitrary reasons a little OTT. You just weren't suited.