I can't speak to your questions but I will offer a couple of ideas. With vertical dropouts chain tension will be a challenge. The problem is you may have to experiment with different chainring/cog combinations to get the chain tight enough. You don't want any slack in that chain. It takes very little slack for the chain to jump off under pressure. For instance if you want, say, about a 70 inch gear you could use 42/16 (71), 40/15 (72), 39/15 (70), etc., each of which will provide slightly different chain tension. But it would be difficult to determine which is best without trying them which would be tedious and possibly expensive. I don't think you can count on a chain tensioner for fixed gear. They are designed for single speed freewheels. If anyone knows of one sturdy enough for fixed gear use I would like to get one. Starting and stopping on a fixed gear puts tremendous stress on the chain, and the tensioners won't take it.

As far as wheels, I just used a handbuilt wheel from Quality Bicycle Products built on a Suzui fixed/free flipflop hub and MA3 rim. Retail is $100. Your LBS can order one from QBP. The fixed side uses a thread on track cog and left hand thread track lockring; the other side doesn't have the thread for the lockring. You can put on a single speed freewheel. An inexpensive way to try it out is just use your existing wheel. Just take off the freewheel, thread on a track cog, and use a bottom bracket lockring to lock it up good and tight. Pedaling forward will constantly tend to tighten it, but resisting to slow down will try to unscrew it. So you have to lock it TIGHT. That's why a track hub has the left hand lockring threads. One day I may spring for a Phil Woods track hub. What a work of art.

If you use Shimano track cogs I believe you can use regular 3/32 inch chain (any 5,6,7,8,9 speed chain) Other cogs may require a 1/8 inch BMX chain.

Too bad you don't live here. I'd give you a Trek 10-speed with horizontal dropouts that I rescued from someone's trash pile Monday. I'm looking for a good home for it. Rainbabe says I can't keep it even though it followed me home.

When you start off on a fixed gear, sit down AS SOON as you start pushing the first pedal down and be prepared for that pedal to come on up. You can't just push the pedal and take your time sitting down. That pedal is going to try to come up and can push you off balance or off the bike. And remember you can't just stop pedalling when you want to slow down. Those feet have to keep moving. It really only takes a few starts/stops to get the hang of this and a couple of days to get really comfortable with it. Then when you ride a freewheel it feels like something is wrong with it. You'll see.

I can't think of anymore right now.
Regards,
Raymond