Is benchpressing helping me lose weight?

Yes. Lower weights, more reps. Cardio is still necessary. Good diet, sleep enough. Eat frequently.
Yes. Weight loss occurs by burning calories while you exercise... Think running or cycling... And it occurs by raising your metabolism... Think weight lifting. Increasing muscle mass helps us burn more calories by increasing our metabolism. Unlike fat, it takes a certain amount of energy to simply maintain muscle. But to lose weight you must burn more calories than you consume... So consume less.