I feel your pain, Chimehk. I had a lot of problems until I watched a local lampworker who also uses a hothead - that made a huge difference. I turned down my torch!!! Now I can even use propane without burning my glass. AND I can even use Moretti clear w/o scum.
Keep trying - turn down the flame and work further out in it.
As for your can lasting for less time.... they are no longer one pound (16 ounces) they are now 14 ounces. Same price, less gas.
Good luck. Keep trying.