Don't Even Know What to Do

I'm in this kinda-sorta relationship with this guy, let me explain... I haven't seen him in a while, from our conversations, I know he likes me a lot. We were just friends for a while because there's a good chunk of distance between us. Over time, though, things started escalating into him calling me terms of endearment. Over Thanksgiving break, I called him out on it. I couldn't take the cute names while being in this sort of relationship limbo. So on Thanksgiving, he asked me what I wanted. I told him the truth--I wanted to date him and there wasn't anyone else I wanted to be with. So we became "exclusive," with him saying, and I quote:

"I want to ask you out but I want it to be a surprise so you have to act surprised. And what I mean by that is if you'll take me as of now I'm exclusively yours but I'm not gonna ask you until I figure out something clever."

So this is all cool and dandy, and I'm probably overthinking this--I'm just a really impatient person. It's just, how long am I supposed to wait? I don't know if he doesn't want to ask yet because of what people will say (he's got a mildly crazy ex and he's a little bit older than me) or because he is genuinely trying to figure out something clever. How long do I wait before attempting to figure it out? Ugh....

And how can he cleverly ask when I'm in Wisconsin and he's in Maine (and isn't visiting till May)?