You probably don't wanna re-boil; you'll boil off all your flavor and aroma hops. However, if you haven't pitched, you wanna do that, like, yesterday; homebrewers never achieve 100% perfect sterilization, so, something is eating that wort, you're gonna wanna get that yeast in there and out-competing it before it gets established.
Presuming you didn't spill a couple of gallons somewhere, it sounds like you're only getting ~40% efficiency into the kettle based on that grain bill end ending up with 6.5 gallons at 1.040. With that much sugar left in the grain, I'd look at a couple aspects of your mashing process:
- Are you hitting and maintaining your mash temperature? Have you recently calibrated your thermometer, so you know you're hitting the temps it says you are?
- Are you mashing for long enough? Give it an hour, and stir vigorously for a minute or two a couple times.
- Are you sparging? What kind of gravity readings are you getting for your first runnings and sparges?
If you really, really don't want a session beer, you can add sugar and/or extract. Probably too late to get to your LHBS tonight, but, it won't hurt to pitch tonight and add more fermentables tomorrow.