Hi JustAGirl and welcome to the board!
Let's take a look at your questions:
My question - after all this build up - is whether or not there is anyway to use my current lenses with the new S2. I fear most likely not and probably because 1.) there is no adaptor to fit 37mm threads onto the S2 and 2.) the lens wouldn't take photographs well because it's too small for the S2. I'm new to adding accessories to my camera though - and after extensive Google searching I can't find any answer to this question! Help!
The standard Canon adaptor for the S2 is 58 mm.
www.lensmateonline.com offer a 58 mm and a 52 mm adaptor. You can also purchase step-up or step-down rings to fit accessories of a different thread size to most lenses.
However, I doubt this could work here. Maybe with the macro lens since it's not THAT small, and maybe (just maybe) the telephoto lens as well since in telephoto mode you have a smaller field of view. That would have to be tested. But I'm almost completely sure the wide lens wouldn't work, you would see dark corners (vignetting) on every pic.
I advise you to contact the people from lensmate (web site I gave you earlier). These people know their accessories very well, they have some lenses for sale, and they can probably give you some good input. Don't expect too much, but you might (just might) have a few good surprises with the macro and tele lenses.
As a side question - is there any reason for me to keep my A75? It's been such a trusty camera I hate to kick it to the curb, but if I can recoop some money by selling it and the lenses to invest in some new lenses for the S2 (if I need to, which I'm thinking I do...) then that's what I want to do...unless there is some good reason to keep it that I'm not aware of being a semi-beginner photographer.
That's really a matter of opinion. The A75 is a good camera, much smaller than the S2, so it can be convenient. But if size is not an issue, then the S2 does everything the A75 does, and more. So I personnally don't see why you would have to keep it. The S2 will not let you down any more than the A75. But I'm simply giving you a rational answer, emotions and convenience can come into play here as well.
Feel free to ask more questions if you need to.