The current loctite/permatex number is 635. This is meant specifically for splines and is slow setting and gap filling.
Do not use thread locking compound on the axle nut. If you insist on doing so, as many do, make bloody sure you lower the applied torque as the recommended torque is based on clean, dry threads. The stub axles are not made of particularly high-zoot steel so DO NOT OVERTORQUE.
There are now hardened bearing spacers available, use them!
Check the splines for wear. If worn replace, period.
Bearings should be a "snug" fit in their bores. Pull, or push, them in square as it is very easy to distort the alloy housing. If they slide in easily but without play, use some press-fit locking compound on the outboard bearing. If there is play, then you will have to get the alloy housing sleeved.
Europa rear wheels are famous for "exiting-stage-left-pursued-by-a-bear" so only use components in good condition and assemble properly.