Recommend a protein supplement?

I'll happily defer to your experience and give front squats a go - I've always been happy to change it up.

At a rough guess, am I looking at 50% - 60% of my normal squat weight?

As an aside - I have a friend that used to oil down female bodybuilders.

Yep i'd say around 50% to start off with and see how you go.
If you still want a nice finishing exercise afterwards, I recommend deep over head barbell squats, with just the barbell, or depending on how brave your feeling stick a little extra weight on, an absolute killer after a hard session.