Savage, I have XP-100s in .223, 7mmBR and .35 Rem. I also have a Super Striker in .308 Win.. To date, I have not found a reliable (safe) way to substantially lighten the trigger pull in the Striker. There are some aftermarket designs, but I have not found them to be safe.
The problem is the long linkage on the Striker trigger. It does not use the same trigger as the Savage rifles. You can reduce the pull by decreasing the sear engagement, but to allow an adequate margin of safety, the best you will be able to do is about 2.5-3 lbs.. I had mine adjusted lighter be a gunsmith, but when I bumped the Striker with my hand, the sear would release. The trigger is a two stage, which takes some getting used to. Savage has developed the Accu-Trigger, but there are no plans to offer it on the Striker line.
The reason you are getting the muzzle flip you complained about stems from the stock design. It places your wrist so far below the axis of the bore the stock acts as a lever flipping the muzzle up. If you compare the Striker to an XP-100 (single shot), you will see the difference. In addition, all of the weight of the Striker is in the grip area, which makes for a very light muzzle.
To make the muzzle more heavy, I milled out a slot in the stock under the bore, and added a slurry of Brownell Steel Bed and lead shot. This increases the overall weight, but really cuts down on the muzzle flip. I also bedded my barrel full length with steel bed, which added a little more weight.
For additional support, you can add a sling swivel stud to the reas of the stock (not the grip). You can then use a tension loop sling around your body, or the back of your neck. By pushing the gun forward against the sling, you will dain some additional stability. I hope this helps.