yes I think heating that much will make the glue soft again,,
yes adding sinew will bring up the weight,,,, try that first before you give up,(many add sinew layers after dry),, it wont hurt anything to add sinew,, gently pull the bow into a little more reflex when you do the next layer,, that being said,, I did do the same thing on a bow I missed weight,, I put more sinew ,, the weight went up,, I did not get much increased performance,, I feel I did not but enough reflex into the bow,,, it still shot well,,