My fears too!! So normal! Its highly unlikely though (he wouldnt have sent you the keys or the note in the first place!).
If he did say any of that you would just simply end the conversation "Gee is that the time? I've got to rush - take care bye". Absolute worst case is him having a baby with someone else. And you would just listen and say "oh that's nice I'm really happy for you, you will make a great dad!... its so funny because I'm really enjoying being single and not committed to anyone or anything" and then get off the phone so you can dissolve in tears. You can do that (and I promise promise promise that he is not going to be telling you that!)
He might tell you that he has met someone he's interested in - just be calm and friendly and happy for him. That's attractive! Remember you are just building the first tiny bridge.
I'm 99.95% certain he is going to be secretly hoping that you would call after he sent the key cause he's been wondering what you've been up to for the last 5 months. He will be happy to hear from you.
