Rest until your knee feels better. Take it slowly and go easier when you get back to it. Most (or all, as a beginner) of your runs should be done at an easy, slower pace. Walk if you need to. I’d also recommend cutting back to 3-4 times per week to start with.

If the knee issues come back, you should check in with a doctor or PT. Don’t ever run through the pain if it gets worse as you go or if it’s affecting your form.

Knee pain is not a normal part of running. You likely need to dial it back a bit. How many miles per week are you running? And are you pushing hard on all your runs?

You won’t lose much (if any) fitness in 2 weeks off, especially if you’re still able to get some cardio in.

You shouldn’t be eating so much food to the point that you feel sick, you mostly just want to transition to eating a higher percentage of carbs in the days leading up to your race. Stuffing yourself to the point that you’re getting acid reflux will be counterproductive.