Quite a list of questions about the subject, many different approaches to getting an airplane flying successfully. Don't know if you live close to where there is a Model r/c club, but that would be my first suggestion and find a person that could get you through the initial difficulties of learning to fly the airplane first. Wouldn't do you any good to do the fpv if the video system fails and your still in the training phase. Getting yourself a slow flying airplane with a big wing would be really beneficial to speeding up the learning curve until you're ready to move up. There is several r/c flight sims available to get you through this if no club is in the local area and for the cost of the sim, will save you twice the cost of replacing/repairing broken airplanes. It also might help you decide which model might be best for carrying the weight of the video equipment.

The other major suggestion is to keep it simple, trying to invent the radio controller all over again can get you creative but there is many reliable radios operating on the 2.4Ghz range since they are locked in by dual receivers and encoded to reduce interference to an absolute minimum. The 1W amp supplied for the 2.4Ghz with the right antenna can give up to over 6 miles of range. There is controllers out there that can be applied through the computer but almost way too much hassle.

Check out some of the companies that deal in FPV equipment and they've already done the hard work for you, found Rangevideo to have reliable products and the best service but there is many other companies that offer equipment to get you into the next phase of flying through the monitor. All I can say is don't overcomplicate the hobby, it's complicated enough without re-inventing the wheel, especially when most of the electronics sold today are getting cheaper and disposable.