The "wiggle room" is over-travel. This is normal. To remove you can buy an ejector housing from Lone Wolf or other sites, that has small set screws drilled into it. These set screws act as "stops" on the trigger bar/sear tab limiting its forward and backward movement , effectively reducing pre-travel and over- travel. You use a small Allen wrench to adjust them. Directions are supplied and you can google it also.
The orange back plate is not needed for your kit to run. The orange backplate is an Armorers backplate and is literally a normal plate cut in half across. When installed This allows you to see the sear engagement operate. Very helpful if you are doing alot of polishing or playing around with trigger configurations to get a lighter trigger.