If you're trying to gain weight, eat the whole eggs. The yolks are healthy and the saturated fat/cholesterol in them has been shown to have no effect on blood cholesterol. But if you can, eat free range or organic, or omega-3 eggs.
As for tuna - yeah, you might want to take some precautions about the mercury. Still, you're eating WAY healthier than the average teen, if I were your mom I'd be counting my lucky stars my kid wasn't living off junk food and getting fat, like so many teens.
If you want to counteract the mercury in tuna, supplement with N-Acetyl-Cysteine - it's very effective for helping the body detoxify from heavy metals. It's also a potent antioxidant.