Hi Mike. I haven't tried it on a K-1, so I can't answer question 1, but hopefully I can help with question 2...
My first copy of this lens had significant front-focusing issues, so I sent that back for replacement. The new copy also front-focuses, requiring -10 AF fine adjustment on my K-3 (my Pentax HD Limited prime lenses require zero adjustment, my Sigma 17-50 f/2.8 requires -4) - however, at that setting it focuses accurately, with one exception... at the longer end (especially 200mm), it still front focuses somewhat at very short distances (2 - 3 metres or thereabouts), but this is only an issue at f/2.8 or so where the depth of field is very shallow. That idiosyncrasy appears to be normal, as another member of our forums sent his copy to Tamron for calibration, and this is exactly how his lens performs following that work. I may still send mine in for calibration too, just to make sure it is as good as it can possibly be on my K-3.
On the subject of general performance... Auto focus is reasonably quick and usually accurate, both in AF-S and AF-C modes. It has the screw drive noise during AF, but is by no means loud. Sharpness at f/2.8 is "ok" (with noticeable softness) but I would really recommend stopping down to f/3.5 - f/4 for generally useable results, and f/5.6 onwards for the best results (by comparison, I have a later model Tamron 70-200 f/2.8 USD in Sony A mount, which is rather decent wide open).
All things considered, I'd say it's a very good lens but not without its quirks - however, when you consider the price, it's something of a bargain. I would recommend that you buy from an authorised dealer so that you can get your lens calibrated free of charge (if required), and avail yourself of the 5 year warranty.
I hope this helps