Replaced faucet, now no cold water

I want to move my utility sink slightly to make room for a support post. A vent pipe for the utility sink is in the way so I want to cut it and attach it to the waste stack about 4 feet above the sink. Photo below shows the current configuration. [ATTACH]77410[/ATTACH] Sorry about the orientation but I couldn't get the photo to import when rotated. :( Anyway,that waste stack supports a full bath and the laundry room on the 1st floor and is also vented next to the toilet. What if any consequences am I looking at ? TIA

Hello Everyone, I have a two part problem but I want to do it one problem at a time. The toilet shut off just keeps spinning, and is stuck on the on position, so i went to down stairs to shut off the valve in the basement that leads to it and the valve in the basement after shutting it off water sprang out from the nut below the handle, so i had to turn it back on and it stopped leaking, why does it leak when i shut this valve off, but stops leaking when i turn it back on? does it need new packing or can i just tighten it up. I put this shutoff valve on myself about 7years ago but only used it once before to shut the water off upstairs, at the time it did not leak when i shut it off. any suggestions i have to shut it off without leaking so i can work on the toilet shutoff. please let me know if you guys have and idea's, that i can try first? Thank you