Mate any meat product in a tin has so much preservatives and salt in its unreal, there's nothing healthy about. If your struggling for time then bulk make things like bolognese, stews, curry's, portion them out and bang in some good carbs like brown rice, sweet potato and veg and bang them in the freezer.
And yes you can do your metabolism some damage in the long run; think about it, your body as a resting metabolic rate (literally how many calories you need to maintain daily activities) you're slashing this plus adding in exercise, the body is shocked and needs to find energy reserves to keep it ticking over. The body will always save fat, so it turns to muscle to provide the energy and will break this down. You're trying to survive off around 300 calories a day, it'll cause you more damage in the long run
You need to increase your calories, I guarantee you'll still shift the weight, plus when the weightloss slows down you have the ability to chip away at deducting more calories from your diet.
To do this I'd add a bit more good source of protein and healthy fats, don't be scared of them they will bulk up the cal count easily (unsalted almonds, walnuts, olive oil, oily fish). Carbs and protein have 4 cals per gram, fats have 9 cal's per gram.
Good and correct nutrition is 80% of the battle, exercise is just giving you the extra boost. Never be discouraged, you'll feel the benefits