Oh, I know, I just felt the need to type that as an answer to those that find the amnesia thing "convenient". Convenient for whom exactly? It's only convenient for the audience, which doesn't really count. It would be convenient if he totally forgot Peter being Spidey and all that, but what happened was actually far from it.
Anyway, I find it justifiable that he'd act like that. As you so well put it in the last page, all the pressure he was feeling for the last oh, let's say, 20 years and getting worse every year, is suddenly gone. It's certainly understandable he would act like the best thing in the world just happened to him.