This sounds exactly like the protocols that I have read about for separation anxiety.
There's only one little thing that concerns me: the exercise where you go outside and then come back in as soon as he starts crying. I'd ask your trainer about the reasoning there. Seems to me that you are rewarding the crying that way. I'd be interested in her explanation about that one!
Otherwise, sounds great. GOOD FOR YOU that you are working sooo hard to help your pup overcome his problem!!! I'm proud of you!