Just worth adding that a one way/check valve can be added in line with the PCV to prevent this and a decent metal one can be picked up cheap easily.you can have instances where the turbo 'boost' not only pressurises the inlet / cylinder but also bleeds through the pcv valve to pressurise the crankcase (or, on Mazda's 1.6 & 1.8L mx5 engines, the camcover) then venting to atmosphere (or wherever?) via the exhaust-side 'breather' pipe
the factory turbo engine used in the Mazda 323 had a different pcv valve to address this - all developed in ~1986...
Just to repeat most of what's been said: With the dipstick popping you've definitely got an over pressurised crankcase, most likely piston rings (from detonation) and/or PCV allowing boost through. Pressure test as suggested will tell you about rings. You definitely want to add the check valve to the PCV regardless. I also agree and wouldn't worry about the turbo at this point.
Regarding fuelling, your RRFPR should means you could have better AFRs than you have (mid-high 12s isn't great for a car with poor cooling, a hot intake and being abused with poor airflow through the radiator aka drifting). 1.8 injectors would help move this in to the right area as a start but it's a slippery slope of sticky plasters of £50 here and there that would be better spent on an ECU and bigger injectors.
My mk1 1.6 uses a 12:1 RRFPR (same vortech but different discs) and could get in to the 11s. I also had a o2 clamp to lessen the lean tip-ins.
I now have an emanage blue piggyback on it to allow me to lengthen injection pulses alongside the 12:1 rrfpr (still on stock 1.6 injectors) and get 11.5 AFRs during boost at 0.5Bar/7psi (and more control over ignition).
Just as some guidance, I bought supra yellow injectors, spare loom, resistors etc to try to push my emanage before realising I should just bite the bullet and do it properly. I've now got a MS3 and 650cc injectors to go on which will mean I never have to worry about any of this sort of stuff again. I wish I'd done that in the first place as would've saved a lot of headaches (and 1 engine I blew up by melting piston rings) along the way! A set of Rx8 injectors and a cheap speeduino would do it for a tighter budget; I'm sure someone must have a base map that would do just as well as any other base map? (i.e. just pig rich with safe ignition).