Sorry, I forgot to answer the part about how far into the straps your feet need to go.
Normally, you just want all you toes sticking out the back side of the strap.
As suggested by CC too far (i.e. the strap back over the ball of your foot is not good because your feet can get trapped in the straps in a bad wipeout and you could suffer an ankle/knee/ hip inury, so it's better not to get the feet in too far.
The trouble with putting the footstrap further forward,, is that this keeps your weight too far forward for the board to really get going easily or for it to get anywhere near it's full speed potential.
So I suggest it's easier to put in slightly more time learning to get back to the best
position on the board than to spend alot of time further forward where you will never see what your board is really capable of.
As for using 1/3 of the boom length and them putting the front line 1 fist forward probably works some of the time with certain sail and certain booms, but I've learned not to trust the "mathematical solutions" for tuning windsurfing gear as very often the design of the sail or the interpretation of the "mathematical solution" results in something that's very unbalanced and people actually learn to deal with signifcant imbalance and soon think that's how a "balanced" rig is supposed to feel.
I get on their gear to see how well it's balanced and either the rig falls forward or back
or it's very front handed or back handed, or it's simply so out of balance I either have to dump the rig or get tossed in the water myself.
That's why setting your lines so you can take your hands off for few seconds at full speed, with the rig all raked back and sheeted in. If the rig just stands there, with your hands off the boom, giving you smooth reliable power you get accustomed to that "really balanced" feeling and it makes your sailing far more "effortless".
Hope this helps,