Yeah a spotter is a MUST if you do heavy bench, and definately prefered with squats even with spotting bars inside a power rack, if you do squats not in a power rack with spotting bars you need a spotter for that to, but DEFINATELY on working sets of bench.
Also, you may want to do some research on failure sets, it may not be productive to do more than one or two failure sets per bodypart per workout
