1) About the engine im guessing its a OS .40 LA dead sticks happen alot when im flying (With an instructor). Did you put the throttle to low that causes alot of my dead sticks. Sometimes my instructor allows me to keep flying until i get a dead stick then he brings it down.
2) One thing he does if im high up make large turns does make any sharp or quick turns take your time line up to the run way (with alot of room to slow down) and slow glide down to the run way.
3) About the leading edge you can usually just take some extra covering and iron/ heat gun it on. But leading edges or dangerous to play with changing the thickness could cause your wings to stall easier and could end up with another crash. Although i doubt some covering will really change that.