I would hesitate to do anything else to the bow at this point if it's holding together. Chalk it up to experience and make a youngster happy by giving it to them for Christmas. Here's why:
1) With three layers of backing, there's an increased potential for fracture. One layer is perfect, but adding more on top actually is anti-productive. Also, tape, paper, linen, burlap, snake skins, etc. won't add any appreciable draw weight to a bow. Sinew and wood will add some weight, but that's a project for your next bow
2) Trying to make a 45 pound bow out of a 25 pounder is really shooting for the moon. Even if you could get backing off and get the back sanded smooth enough to accept a wooden backing strip, you wouldn't be able to get a 20 pound increase without breaking the bow. At best, you'd have a bow that is still way under weight (by 10 pounds or more) and that would probably take a significant amount of set.
3) You can pike (shorten) a bow to increase the draw weight, but again, you wouldn't be able to safely get anywhere near 45 pounds at a normal draw length with this bow. For the future, however, taking 1" off each tip (for a total reduction in length of 2") will equate to roughly a 5# increase in draw weight.
Get yourself another board or stave and make some more shavings! Keep it up!