What bike did you have previous to the K13? Did you get a chance to test-ride one of these for a while to get a feel for the ergonomics? Do not mount pegs on your fairings... looks terrible, few would buy the bike/poor trade value, and if you drop the thing you'll have major damage to fairings. Plus with the forward lean and stretched-out legs you may find that the tight "flying C" position is even worse.
I'm average size, but almost any bike requires period of adaptation and that was especially true of the K13S because it was my first bike that had semi-aggressive sport ergos. Had lots of pain in palms, wrists, elbows and stiffness in knees due to neck trauma from accidents, but as I rode the bike more and more and over long distances the pain went away. The bike has been very comfortable for a long while now and have been on 600mi/day rides, though every 200mi one gets a stretch-out at refills and potty breaks.
The only adjustment I've ever had to make is using a Throttle Rocker to reduce wrist tension on the stiffer BMW throttle spring compared to previous Suzukis.
150-mi upward rides on commonplace for me and have put over 20K miles on the bike in year and quarter. A motorcycle is essentially primary transportation to me; car gets used during rain and moving large objects/trailering.
Give yourself more time and long rides. If nothing improves, you probably should have bought a K13GT.