If it's not leaking, leave the power tube alone for now. The bronze spring is just the original spacer for the level seven bolt; it may wear out eventually and you can replace it with another or a spacer.
Don't tempt fate by making your velocity adjuster vent on over pressure.
First, did you give it oil when you had it apart? Four drops in the ASA is a fair start, or two or three in the banjo bolt port.
You need about 1000 psi on a bottle gauge at least to really debug a mag. You might try borrowing a bottle if you don't have a gauge on an ASA that will tell you what yours does. Old bottle regs can be farty as much and any other.
At the moment, you should probably order an RT rebuild kit from airgundesignsusa.com, since tunamart is a bit occupied. I think they still have RT kits(?). yeah, RT O-Ring Replacement Kit
Old urethane o-rings can get hard instead of mushy, making them bind up instead of leak, so if any of them looked dark or hard, you might just as well rebuild it.
Also, take the valve out and make sure the bolt (without the spring) drops though the body washer without a problem. While my RT was pretty clean, the body washer had a few years of corrosion/paint reside on it that sanded off relatively easily. Still, it needed to be sanded off.
If you're not leaking and you're RT'ing sometimes, you're not far off the mark.
If you haven't checked, the bolt spring should be at least 1/8" longer than the end of the bolt. 3/16" - 14" over is a fresh spring. Flush with the tip is getting into problems.