Sweet Bentley just diagnosed with Diabetes at 7yrs old

Hi everyone!

Just a little overwhelmed and need some advice, but i am not even sure what to ask

Our 7yr old Bentley (german sheppard rottweiler mix) was just diagnosed yesterday with diabetes-we only adopted him last october

Our vet/vet tech were so miserable and treated us like our questions were annoying/bothering them

We spent today learning how to administer the shots, but still feel a little lost about what life looks like here on out

We start his insulin shots tomorrow (12units x 2 a day) but were not given any information about what he will be like during the treatment or what to feed him or how often we can give him treats (and he deserves all the treats because he is the BEST boy)

Hes been peeing in his sleep, not as interested in walks, and went from 47kg to 43kg in a matter of weeks

Typically we give him liver bites and dehydrated beef and dehydrated chicken from costco (i try and buy things with the least amount of ingredients)

Will our boy come back to how he was? Playful and ready for walks? Will the pee in his sleep stop? Its heart breaking to see him so ashamed of himself for something he cant help

Just dont know what to do or prepare ourselves for how to track his details, or what ingredients to look out for/avoid/increase

Anything is a huge help-we are sad but optimistic