I don't think you can average you arm strenght into your running checks.
I see you (OP) has modified your char. I'd advise against a Body of 4. Have it on 3 or 5. So preferably 5. Lower strenght to 1, buy it up to 2 (or 3 even). Spend the 2 points on Body to 5 and Agi to 3. I don't think buying firearms 6 is worth it and that would save you the karma.
Or just move 1 point from Int to Bod if you don't want to ditch Firearms 6.