Hi sorry but I don't wish to affend you, but at 19 why do you want to get yourself involved with a man of 25 with 2 kids??
He has baggage, and you are so young, you don't need to accept someone (unless they are exceptionally nice to you) with so much baggage.
Along with that, he sounds slightely disturbed, sorry, but to slash the tyres of his girlfreind! if he was 19 like yourself, I would say cause he is young, but at 25 with two kids, well he should know better!
Maybe he has got back with the childrens mother, maybe he has met someone else, who cares, the main thing is he has done you one BIG favor.
Forget him, and meet someone who will treat you with respect and love.