You're not the first person with the Gas Tube issue thanks to the Tapco stock "upgrade" which includes a replacement gas tube that's often out of spec:
http://www.gunandgame.com/forums/sks/47 ... oblem.htmlhttp://www.thehighroad.org/archive/inde ... 03696.htmlhttp://www.calguns.net/calgunforum/show ... p?t=483348Seriously, rip that crappy Tapco stock set off and put the original wood and gas-tube back on the gun. Hopefully you didn't remove enough metal from the receiver trying to fit the Tapco gas tube unit that it's beyond repair, if the rifle doesn't function properly with the original gas tube (with the wooden top handguard attached) installed you are pretty much screwed ...
The more troubling aspect of this is the unintentional/negligent discharge... The SKS has a very obvious safety mounted on the trigger guard, was this engaged (flipped "up") when the gun fired in your tree stand? Did you simply bump the rifle against the base of your stand when it discharged? It could be a number of problems including a stuck firing pin (rusted/bent so the pin protrudes from the bolt, if this is the case you are lucky you did not get 10 rounds in the face when you dropped the bolt into battery), prior trigger modifications by a previous owner, etc... If you are going to own and operate a surplus gun like this you HAVE to understand how to completely strip and clean it, including tearing the bolt apart to remove the firing pin, extractor, etc... Most of these were soaked with cosmoline (a thick, jelly like preservative grease) that has to be removed from nooks and crannys to operate safely - simply blasting some bore cleaner into the bolt and trigger mechanism is not going to cut it. The Yugoslavian models (with the funny flip-up grenade launcher sights) are notorious for firing pin/internal rust problems that can make them unsafe without proper cleaning and maintenance before shooting them for the first time and are very common in the current marketplace.
There are a TON of resources available on how to completely disassemble and service the SKS rifle, Google is your friend, they are one of the easier milsurp rifles to break down and completely clean in my experience if you are willing to spend the time. A new wooden stock for the rifle is only $25 (
http://tickbitesupply.com/sksstk.html) and would probably be a better direction than continuing to fool with the Tapco aftermarket upgrades. The SKS is well designed and reliable in it's original form when properly cleaned and maintained, there's pretty much no functional improvement in the weapon that comes from adding anything Tapco to the gun but a large risk of making it less reliable.
My honest advice at this point... if you are in over your head, sell/trade the rifle to someone who knows the SKS platform and wants a parts/project rifle and chalk it up as a lesson learned - save your pennies for a value priced hunting bolt or level action rifle like the Remington 700 ADL/Marlin XS7 (scoped kits for $400), Marlin 336 lever action ($400 or less new), etc...