Welcome to the forum AxisRod! Should start with the disclaimer that I am very new to shooting so please take my suggestions and experience with a grain of salt.

First, I have a 7mm-08 as well and tried using the exact same led sled/setup when I first started shooting and had the same terrible results. For whatever reason, it seemed next to impossible to get behind that thing and get comfortable. Maybe try a new setup with a decent front rest and a rear bag or rear rest that may help some. Also, I noticed you said you only had about 60 rounds down the tube, but you have already tried 4 different types of ammo. So did you change your zero on your scope every time you changed ammunition? I was told recently that when you change bullet manufacture, weight and even primer in some cases that you should re-zero your scope. Reason being that it will affect your point of impact. So if you zeroed with 120gr, Barnes Vor-Tx and then after 10 shots switched to the 140gr Winchester it may have moved you off your POI ever so slightly.

Next, as you probably know there are a multitude of opinions on barrel break-in and I won't start a discussion here. My suggestion is pick some decent ammo like the Barnes, zero your rifle, practice good fundamentals, and give it 40 rounds or so and see if your gun settles in. Many claim that it takes 60-80 shots just to get your barrel in a condition where it will shoot with proper accuracy, although I do not know if that it true or not.

Can you post some your groups? Some of the more experienced members here may be better able to diagnose the issue by looking the vertical and/or horizontal dispersion of your shots.

Good luck and keep us updated.