Re: Bite block. You should have your mouth open about an inch wide. That should allow them to keep their seal even while speaking to someone or while eating. The two-inch recommendations that I've read from some other manufacturers are generally directed at emotive singers who tend to really open wide on some of their stronger notes. I'm pretty sure that an inch or so will do you just fine.
So roughly the width of two fingers on top of one another stuck in my mouth should be more then enough.