Welcome to the Starboard WS School forum.
Can you tell us what brand/model your 6.5 m2 sail, and what brand and length/MCS/IMCS your mast is?
Your higher wind issues could be associated with how you are rigging your sail, or possibly some sort of technique issue.
Are you using a harness yet?
"Pushing" with the front hand usually means you are using a harness and your harness lines are incorrectly balanced.
When your sail is correctly rigged, and your harness lines are correctly balanced you normally would never need to "push" with your front hand.
Also, if you remember what your sail looked like last time you rigged it, where was the front of the batten above the boom relative the the fore and aft centerline of the mast.
If well forward of the front of the mast, you don't have nearly enough downhaul and you aren't getting the mast bent enough as a result of less than required downhaul.
If the front of the batten above the boom is pulled back to about the center of the mast, then your mast bend and downhaul would seem to be about right.
If the batten above the boom is well behind the back of the mast then you may have excessive downhaul and your sail may be "over flattened" which reduces the power in the sail, but may also make the sail very unstable and hard to handle.
Also what mast base extension are you using..... the brand and the amount of extension you normally use.
Hope this helps,