You can go to the RAW site and see his gauge and quick fill blocks. He even has a section that you can see the 2 types of bottle adapters l. Yours should be the Theoben. But look to make sure. He even has the bottle adaper.
Leaking bottles when off are a common issue over time but once on the bottle cause no issues. Marring has the bottle orings. There is a trick to getting the bottles off under pressure and I think he has that listed on how to do this.
Just a heads up if you do not know this, to remove the stock for what ever reason the bottle must be removed.
14.3 shoot great as you mentioned in these guns. But the JSB 13.73 will.shoot just as good.
One other thing is if you buy the fill and gauge adapter to will have to work the stock for the set up. Not hard to do.
That gun should be a laser if set up correct. Hard to cock with much hammer cranked in is common. You might concede ordering a new hammer spring. A good cleaning and a very light lube may help also. Love the 20 caliber.
I would check the barrel bolts also and clean the barrel. I fine the most .20 with good fps are louder than most. Ldc will fix that. JMO I do shoot the .20 and have had many spring and pcp guns.