i try to give you a hand on this.
.40 glass is enough for 50 lbs.
go with smooth-on,its the best you can get,
and proven by thousands of bowyers.
for the hotbox...
I wouldnt do it without one.epoxy needs heat while it hardens.you simply need some kind of box and some light bulbs,thats it.flip an old (or brand new,if you like)cabinet 90 degrees put 3 or 4 100 watt lamps inside and heat the damm thing.
no cabinet?
2 chairs,2 sticks from one chair to the other and through some blankets over them,again some heatsource and it gets warm.
any simple idea like that will work.
take care not to burn down the house tho,so while the thing is running,watch it.
if you still need help,ask.
we are here to help.
shantam