Heaviest bow pulled from someone under 18 I know, is Joseph Gibbs when he was that age. Don't remember exactly, but I think he said he pulled 170# at the age of 17. Eirik Diserud pulled a 143#@32" yew just before he turned 18. Also there were this Duch boy at 15 pulling 130#@32" with ease last year at Batsford.
-You are in a fine league, there's not many people your age pulling theese bows
As for your lamination project I think I would have tried bamboo for the back. Perfect hickory or ash (at least northern European ash) would also work, but boo would have been the best.
I don't know what you have as local wood, but there are more woods than yew that makes heavy warbows. If you have access to wytch elm, laburnum, osage, BL or good ash, they all make good warbows.
For laminating, try to use something a little less compression strong than ipe, and you will not overpower the backing wood so much. Ash, hickory, birch, hazel etc. backing plus several types of oak as a belly is a good combination, and often easy accessable.