Outside spigot has low water pressure and sputters when fully opened.
I have low water pressure at an outside spigot, while every other fixture in the house has strong pressure. The outside spigot can be traced to an old gate valve on copper pipe inside. When I close the indoor valve fully, the handle won’t turn further, but the spigot outside still gets some flow but it’s weak. When I try turning it the indoor valve counterclockwise to open it more, I feel it move and immediately see water dripping from right below the brass packing nut.
Regarding the outside spigot itself: when I open it all the way, it actually sputters and loses pressure. It runs best somewhere in the middle, between fully closed and fully open.
To make it more fun, access is tight with the valve sitting right under the bathroom, directly above the toilet and sink drain pipes, so there’s not a lot of room to work or maneuver a torch/pipe cutter in there.
I’m decently-handy but not the best with plumbing, soldering and cutting pipe. Thoughts on what to do here? Call a pro or DIY? Thanks for the help in advance.