The /6 breather is a fiber washer held by light spring pressure. You can polish the washer for better seal. You can addjust the spring for more pressure. You can get or make a thicker washer, or glue a thin disc of rubber on the bottom of the washer. Or you can replace the /6 breather with the later type leaf type breather. None of this will resolve an issue of excess blow by.
I think I would want to do a leak down test on the cylinders just to verify compression losses that may be the seat of the issue.
Worn valve guides can be confirmed by turning the crank until the valve opens but a few milimeters, then pushing the top of the valve forward and back to see how much play you got. A coupla milimeters at the top of the valve is OK. More than that and best budget for valve guides replacement.
The exh valve guides tend to wear out much faster than the intakes. Just much higher heat means more wear.