You can't overfeed by feeding two complete foods, but you do have to be careful with complimentary as they need to be part of a balanced diet (should make up no more than 10% of the diet) or you are risking nutrition issues. I read years ago that 20g of dry food is equivalent to one pouch of wet, and have worked on that logic ever since, so in theory you are feeding him the equivalent of just over 3 pouches. Ideally, you should feed for what they should weigh rather than what they do, however you can't reduce their food intake by more than 10% without risking health issues, so this should be done gradually. I would reduce the dry rather than the wet, as dry contains more calories and a purely dry food isn't ideal for male cats and overweight males are more at risk of urinary issues.
Good luck, we've pretty much given up trying to get my overweight cat to lose weight!