Good morning!
I can only answer for what I have experienced and seen in my part of the world (Germany), but nonetheless:
1. Are instructors given a salary/wage that is commensurate to their length of training/financial commitment/experience?
No and yes. No if one considers the very low salary/hourly rate for PPL instructors. Yes, once they progress to instrument, multi engine, type-rating instruction.
2. Compared to other careers paths, is the salary/wage for a position as an instructor attractive?
Not really. (With the exception of some very well paid instructors within the training organisation of our flag carrier maybe.)
3. Is the career path of flight instructing widely seen as a stepping stone to get entry into a career in the airlines?
Not here. Single engine VFR time counts near to nothing, no matter if flown privately or as an instructor.
4. Due to the inherent forces acting upon more experienced pilots to gravitate towards airline employment, is there a lack of experience in GA or flight instruction?
In GA certainly so, at least in times of high demand (not now, obviously). In flight instruction, I can't see that lack of experience, as most flight instructors are either doing it beside their normal airline/GA activity or after their (sometimes forced) retirement or during breaks in their employment. At least where I have instructed during the last 20 years.
5. Do you think that many perceive a career in flight instruction as demeaning, or of lower prestige, than a career in an airline?
Yes, certainly. That's why you find very few full-time "career" instructors here, but mostly professionals who instruct in their free time.
Regards, max