drag and drop should work, just make sure its open on the 'log' window (top left button), definitely works as i use it myself, in v7 it'll be a lot more commandline orientated and heavily customisable
as for the yara stuff, i'll see what i can do, worst case i can make it a plugin style kinda thing, just have to look at how yara works under the hood etc..
server error - i'd have to check up with empire on that but usually it automagically fixes itself