Allen called Tom, but why? *spoilers*

Allen called Tom and asked if he was going to be available to talk the next day.
When Tom got there Allen told him to get out of here and Allen was shot by Wally. Wally and Graeber had no clue Allen was going to tip Tom off, so why was he shot?

Was a conclusion ever drawn with the paint they found on Summer's hands?

Did we ever get an explanation with the bite marks on Summer's hands. Who did it?

We know Will was arrested at the golf course, but what evidence do we have that he killed Summer?