[Q] HELP battery drain and outer glass screen replacement topic

hi all I installed many roms and finally kept CM 11 with fly on mod tweaks

but I have two issues hope help me

first while turning off the phone and charging it , the battery gives me 5% charged but when turn on the phone i found its like 60% already charged


so what may be the Reason? I want to keep the battery for long time



second , my outer glass is damaged, i found many youtube videos for replacement seems not too hard not too easy,
but do i need LCD glue for it?? or as many videos i saw they put double shift adehesive and put the screen then heat on it and press only

so which is better to do ?? thanks All for their nice contributions and posts