One of the 0.05uF caps is measuring 0.2uF, one of the 0.1uF measures 0.4uF....so I'm guessing they're bad.
Capacitors generally do not increase capacitance when they go bad. Are you measuring in circuit or out of circuit? Any chance there could be other devices in parallel?
Do the capacitors have tolerances marked on them like modern caps do? Even modern caps are often marked -20/+80%, so it wouldn't be surprising if old caps had a pretty wide tolerance to start with. Not +300% wide, so something else is going on with the 0.1uF measuring 0.4uF.
Is it marked? Any chance someone else changed it for a larger value years ago?
I could put two in parallel for the 0.05uf ones
Two 0.1uF capacitors in parallel is 0.2uF. Two 0.1uF capacitors in series is 0.05uF, but as someone else pointed out, just use the modern standard value of 0.047uF.
still not sure what to do on that 0.01uf 600v
Film capacitors for tube circuits are not that difficult to find. The first place I checked has 630V film caps in stock:
https://www.tubesandmore.com/products/capacitors?filters=3109a3115Where are you looking that you can't find a 0.01uF cap with 600V or more rating?
I even checked Digikey, searching for 0.01uF/630V film cap has 113 different part numbers in stock. Not exactly a hard to find specialty item.
Are the domino caps (never seen one of those before, I don't generally work on antique gear) the ones marked 50MMF in the schematics? I guess that would be 50pF mica in modern notation?
Leaky implies that the DC resistance value has decreased. A Fluke 87V is perfect for measuring resistance, just clip the leads on the cap and let it sit for a while. Make sure you don't hold the leads on with your hands, your skin resistance is too low to measure cap leakage accurately, you need clips. Make sure you wait for the reading to stabilize, trying to measure resistance of capacitors gives nonsensical results until the cap charges up to the measurement voltage (could take quite a while to stabilize with larger capacitance values).
As others pointed out definitely replace all the electrolytics, nothing wrong with replacing the film caps as well but they don't often go bad if they haven't been severely abused. This amp is a decade or two older than anything I've messed with, so maybe that era of caps had an eventual environmental susceptibility that shows up, like moisture absorption or something, so I'll defer to those that have actually rebuilt some equipment this old on how strongly it would be recommended to replace any old (1950's?) film caps.
