You may want to read the back of your dog food and see what the directions say.
Each food has it’s own amount by the size of your animal .
I personally have always just left the bowl full at all times they learn to eat what they need and leave he rest.
I to have a black lab and she is just about the same weight 60/65 lbs. Very good health and the bowl is always full.

Twice a day with treats in between should be fine. I have a Husky/Lab mix and that's what I fed her when she was 5 years old. Too much and they gain weight fast. At 5 years, you could give your dog a small meal inbetween her two big meals of the day.

You should at least feed him twice a day

Well my dog eats all the time so we keep his dog dish full.