Hmmmmmmm..... " I gave it regular downhaul and tons of outhaul and somehow survived these violent 7B gusts"...........?
Just a hint here:
If you add alot more downhaul, you open up the top of the sail, so it handles gusts better, and has less power from top to bottom overall.
If you add alot more outhaul (as you did in this case it sounds like) you only flatten the lower panels of the sail and the top of the sail retains alot of power and rigidity that you really don't want (or need).
So, next time you need to "shrink" the size of your 7.5 m2 try using alot more downhaul, and then add a bit more than normal outhaul.
This will prevent your sail from becoming "on/off" and take away alot of the overall power and "pitchiness" due to having the top full and the lower panels flattened.
On your boom height/ harness line length, you can lower the boom, but you need to cut the tubing on your harness lines so you can shorten the lines as well.
Harness line length is dependent alot on the length of your arms (and other factors) so when you lower the boom, you lean out away from the rig further, to the extent of your arm length, but your hips stay closer to the rig so you need to shorten your lines.
Also, on a wide board like the F-Type, you can really get away with shorter harness lines than you would think. Wider boards do not necessarily equal longer harness lines.
Your body is further off the centerline, so you can exert more leverage on the rig.
As far as the catapaults while you are getting your back foot into the rear footstrap, try to judge any upcoming gusts, and don't lift your foot to put it into the strap until you have all your weight on the rig so you won't get catapaulted.
As you get more experience, you will find that getting into the rear strap, without a catapault involved, will get much easier. The fear is something you just have to "deal with" right now, but soon you will be beyond being scared.
Hope this helps,