Hi!
Having an engine that leaks fuel out through the front bearing is something you have to live with occasionally as it depends on the crankshaft to engine housing fit...not to if the ballbearing is bad or if it is shielded or not. That is a misconception among many modelers.

My advise to you is to use a milder fuel...let's say 5%nitro and 20% castor oil(or a mix of castor and synthetic oil).
There are some engines that can't tolerate as much nitro as 15% nitro as their combustion chamber is to small (they have too high compression built in). Symptoms using too much nitro is very finicky high speed needle settings and engine could abruptly stop at high or low throttle settings.
A suitable prop is a 11x5 or 11x6 APC (if you fly at sea level) Not a 10x6!
And a suitable glowplug is an Enya 3 or OS 8 glowplug.

Regards!
Jan K
Sweden