I used to live in Canada, so I've crossed the border hundreds of times both ways, as both an American and a Canadian resident. Usually it's pretty perfunctory. Especially at Windsor, which is always really busy. Canadian Customs officials at Windsor are kind of assholes (there and Pearson Airport are the rudest in my experience) but also usually in a hurry to get you on through. Every time I've actually been pulled in and questioned or had my car searched has been at a less busy rural crossing. Just don't overthink their questions or try to be clever. Answer simply and directly. Sometimes they will throw in oddball questions to try and trip you up, like asking where you work or something. Or instead of asking first where you live, ask where you were born -- that always trips me up when they reverse that order: "Colu -- er, Cincinnati, Ohio."
Generally, if you're just going to travel and sightsee, they don't ask much. I've found that it generates a lot of suspicion when I say I'm going to visit friends, which is typically why I go to Canada these days, because I guess they think that if you know people there, you might be trying to stay illegally. That's when they start asking about my job and so on, I guess to try and suss out what commitments I have here that I would be going back for.
I'd be really surprised if they asked for proof of how much is in your checking account. I don't think they even checked that when I was moving to Canada on a student visa.
Ohio ID will generally work okay in bars or liquor stores, although if you're young-looking, you might get the occasional person who questions it. Having your passport on you would back it up, but so would any other library card or credit card or whatever that shows evidence that you do live in Ohio. But in general they don't card much there.
7AM will probably be a less busy time at Windsor. I have really avoided the Ambassador Bridge the past decade or so because it is almost always really backed up. The Detroit-Windsor tunnel is often not as bad. Usually, when I'm going on across to Toronto or other points east of London, I just go around Detroit and cross at Port Huron-Sarnia because it's usually not as busy. But 7AM on a weekend might be one of the few times the Ambassador Bridge isn't too bad. I did use it last summer and I think it was a Sunday morning and the wait wasn't too bad.