don't attempt an embouchure remake -- simply do as many people recommend on this forum and play lots of long low notes quietly. Your embouchure will naturally evolve to the best formation. And stop stressing about range -- you need to take things gradually and be patient. The Complete Solfeggi by Concone (published by Balquhidder Music) is a great book to work out of in my opinion because all the exercises can be played slowly and you can work on tone, air-flow, comfort, etc, without obsessing over difficult rhythms, difficult key signatures and range. Combine that book with Arban (Eric Bolvin has a terrific guide to the Arban method for sale at his web-site which can help you a lot to get the most out of the Arban method) and a regular schedule of daily practice, with warmups and pacing yourself (rest as much as you play) and you should be just fine. And get yourself a good teacher as soon as you can -- nothing can take the place of having a person right there observing everything you do and offering advice as to how you might change things to play better. And as for being stuck in a hole -- quite often the hole we're stuck in is in our heads and not in the physical world. Just a change of practice regime and you might find you start advancing to where you want to be.