On the main thread topic: The wording indicates that a Qi Focus adds to the level instead of the end total being limited to Magic rating, but I would be inclined to limit the end total to Magic rating just to keep headaches from occurring even if that would just be a house rule.
I don't have the SR5 book right now (my group only has one and it gets passed around), so I would appreciate enlightenment as to what might be different in 5E, but in S4A 256-257 it talks about addiction resistance Will+Logic (for mental addictions) or Body+Will (for physical addictions) with a threshold of the substance. Focus Addiction is mentioned in SM 27 but unfortunately doesn't give any ground rules for thresholds.
I remember that S4A states that you can bind up to (Logic) foci, but I can't find anything that clearly states what constitutes addiction-risk behavior besides the general behavior patterns in S4A 93. I noticed the reference to a more serious addiction to a F30 foci, but I think it would be the frequency that you use it that sets up a person for addiction more than force - though force might still have something to do with it. However, spells complicate things because the addiction threshold table lists tripchip BTLs as "only" 3, which would be the equivalent to the Force of a weak magic spell. Should magic/foci threshold instead be Force/Magic? Or Force/2?