excessive blowby

[ktbtrucking]

Would excessive blowby cause combustion gases go into valve area?
truck has 1.2m miles
boost dropped from 34psi to around 25psi currently and i would say EGT is down around 100F(so now i have around 400-500 cannot pass 800 climbing hills)
developed some oil leak at the back of an engine ,figured out is is from under rocker cover , tighten the screwes and now i have oil leak from driver side behind ecm and passanger side around thermostat housing,
popped the valve cover on hot engine and when cranking/running engine without cover have smoke coming out of driver corner top and bottom next to camshaft on driver side
I know the engine is worn out but any thoughts are appreciated.
Will try to test integrity off intake side over the weekend for leaks.
Exhaust side pressure dropped from 150 to 110 too on insite.
The blowby tube is not restricted and i have steady flow from there with leaking oil,too.
On running engine when i remove the cap from oil feel tube and put a hand there i feel a nice buildup of pressure.