1. Don't use ethanol as the solvent. I could tell you right now that mixing ethanol and hypochlorite gives chloroform and sodium formate via the haloform reaction. That reaction doesn't happen immediately, only upon heating, and that's when the reaction goes uncontrollable! With adding hydrochloric acid into the mix, I'm sure you'd get that undesireable reaction to start at room temperature, and you'd get chloroform & formic acid. You could use a different solvent, like acetic acid or ...
2. What I'd recommend that you do, is go out and get some 10% NaOCl pool bleach and use that instead. In working, trying to make chloroform from acetone, I originally tried Ca(OCl)2. The solids formed in the reaction were a bitch. I went to 10% NaOCl, and it went wonderfully. Don't use the ethanol solvent either! It seemed to oxidize quite effectively in the presence of free chlorine. You should be able to oxidize THF to GBL in a solventless condition. Good luck on finding the right reaction parameters... I've got some ideas, but don't want to tout them as "the way to do it", because I've got no experience with the method.
3. In my experience, distilling GBL at atmospheric pressure will give you a distillate that is not colorless. I bet <<1% decomposes, so it's not a big deal in terms of losses.