http://petsci.co.uk/feline-calorie-calculator/
The above link will allow you to calculate the calories for Mayton, I just put the details you gave, if he was at his ideal weight 15lbs and you wanted him to maintain it comes out at 354kCal, but since he is a little below, you might want to give him a teeny bit more, until he gets to a good weight for him.
Bear in mind that how much he needs will be individual for him, the way to monitor if he is getting enough would be to regularly weigh him, I do this with George, I haven't got a special scale, just use the human scale hop on with him, then subtract my weight to get Georges weight, you will need to let the scales be your guide.
Another thing to note on the SS is when you've got ketone test and what the result is, great that he has been negative for a while.
How's Mayton overall now, I read through your earlier posts and it seems he was a very poorly kitty back in Novem/december?
Is he peeing lots? Less now than before?
How about drinking?? hanging out at the water bowl loads? or has he began to behave more normally?
You've been doing a great job with the tests amps and pmps and running the curves, but I would recommend getting spot checks as and when you can and if you could get mum on board, all the better, getting a before bed test every night would also be really helpful.
Running curves once a week, with no other midcycle data on other days can be deceiving, if the curve is run on a bounce cycle, what you'll get is relatively high flat numbers, so it can make it seem as though kitty might need more insulin, some cats BG can drop hard and fast in the first half of the cycle and be right up into the pinks by next ps, as the dosing is based on how low the dose can get kitty, it is useful to get those spot checks in they will help when it comes to the point of making a dosing change.
I would encourage you to look at the ss in other peoples sig blocks, some of us test more, others less, but it will give you an idea of what we are talking about. The stickies that others have pointed out are also full of lots of great info and pointers, keep asking questions.
Oh and one last thing, guess in all the excitement we forgot to give your dad the BOS award, given when CG shoots their first green

