Help with Club setup and grip

[Hacker-G]

I'm new to golf as a serious hobby/pastime, and this is the first time I've tried out some of my new clubs.

So I spent a couple of hours at the driving range yesterday and notice 2 things that I would like help with:

1) my grip . When I got home, I had a huge blister on my right hand (I'm a righty, so the hand without the glove) -- on the middle, finger bottom joint just above the palm. Not quite sure why I would get blister on this hand, and in this position of my grip (i do an interlocking grip where the left index finger fits inbetween the pinkie and ring finger of the right hand). Anybody have ideas how I got this blister? Does this suggest a weak grip, or a too thin grip thickness (my hand length from wrist to top of middle finger is ~8")?

2) my clubs . Whereas I was getting a fair amount of inconsitency with my irons (all of them), I found I was nailing my 3H straight and long reproducibly. What I don't know is whether this is natural, or whether this is due to the difference in a) the length of the club, or b) the stiffness of the club. My irons are Diablo Edges (uniflex steel), and my 3H is a TM Superfast Burner 2.0 (stiff).

At the range, I was hitting my 5i to 185 yards, my 8i to 150yards and my 3H out to 215 yards. That's pretty much all I have in terms of distance and indication of swing speed. Since the 3H felt infinitely better and I had significantly more control of it, I wonder whether this suggests I should be playing with a stiffer and/or longer shaft on the clubs? I felt the length of the 3H was more comfortable for me, with the clubs (standard length and lie) feeling 1/2 inch short or so. Felt like I had to bend a little more than I would like, so wonder if I could use a slightly longer shaft?

I have been to a fitter to get myself fit, but the person there said that it would be impossible to fit me until I had a consistent swing. SO, I've not been able to get fitted. FYI, I'm 6'1" with a wrist height of 35".

Any suggestions? I do have a 15 day return policy on the clubs at Callaway PreOwned, so I wonder whether I should return the clubs and maybe get another set that is stiffer shaft and 1/2" longer?

[Hacker-G]

Any suggestions at all?