Ahhh...the 7x57!! I miss mine a little. Mine was as finicky as anything I've ever loaded for (which has been a BUNCH), but like you I enjoyed the process and it taught me that sometimes subtle changes are all you need.
If anyone handed me a 7x57 today, I would start with a 140 or 150gr bullet and 4350 powder - just like you did. I went through several different 140s and 150s with mine with mediocre results. One day I split the difference and dropped the 145gr Speer in the case with the same powder, and my groups were immediately cut by 75% or so, including some cloverleaf groups at 100 yards. Same with the 150 to 160gr bullets. I shot several 150's and 160's with ok results, then one day loaded the 154gr Hornady and things got much better. Then instead of 4350 or something ike RL19, I used W760 and those 154s starting printing groups any hunter would love. I swore off W760 because of how it used to act in hot temperatures, but I just needed to be smarter when using it. Don't max it out in the winter only to see higher pressures in the summer. Do the opposite.
Seeing how you have a bunch of Varget, it may not be bad with 140s, but considering the burn rate of that powder and the 7x57 case, try something like the 120gr class bullet and that powder. If you are looking for a hunting load, that probably means something like the lighter Barnes TSX.
