Hi Sally! I am sorry to hear things are tough at the moment & I can imagine the pressure you are under wanting to have this fixed before the new bub arrives.
He's obviously very overtired & you're right, the 2-1 transition probably doesn't help. At 16 months he "should" be able to handle longer A times so it would help have his clock set on 1 nap. I would suggest the following routine:
5am - wakes up
10-10.30am - morning nap
12-12.30pm - nap ends
5.30-6pm - bedtime
The bedtime is very early but I strongly believe that it will help erase overtiredness. It will also mean that when he wakes in the morning he will be better rested & then you can work towards pushing the whole day forward in 15-20min increments & finally come to a 7-7 day. If you can see he is miserable 3-4hrs into the morning, then you might want to try 2 naps. If you do so, I would recommend you shorten the morning nap so that he is taking a longer pm nap & can go to bed a little later. ON a 2-nap day his schedule might look something like this:
9.30-10am - morning nap (you will have to wake him)
1-2.30 - afternoon nap (generally 1.5hrs)
7pm - bedtime
Some babies at this age will flat out refuse a pm nap (or it will still be short) even on a 30min catnap & although some have had success with shortening the morning nap even further, it didn't work for us. If you aren't comfortable waking him up in the morning, let him sleep & do a super early bedtime.
Sleep training - this is the hard part!!! I know you want to go towards the GW method & like you said at the moment you are at the door stage but if your presence is stalling bedtime & he is up every minute checking if you are there, then you are a prop & you need to start taking yourself away from the picture. You might want to try telling him you'll be back & leaving the room to see how he will go. Him crying is normal & I don't think you should see it as abandoning him. With the wi/wo method, they will cry but its not the same as cio/cc because you return at every count to reassure him that you are NOT leaving him but at the same time giving him the message that its bedtime. Sleep training can take a while though so I would stick to it for 2 weeks before assesing if its working or not.
Him waking up in the morning is a combination of being dependant on you to get back to sleep as well as being overtired. So for the morning wake up, I would also suggest the wi/wo method until your desired wake up time (say 6am for now).
I have cried on and off all day so ashamed of myself for letting my little boy go through that, poor little mite won't have known why on earth his mummy and daddy weren't helping him.
Please don't give yourself a hard time about it. I did the very same thing... but worse... I let her cio when she was just 14months for an hour at night. I know the guilt you are feeling but please don't!
It might seem impossible now to think that he will sleep through the night but believe me, he will. You can do this!!! You just have to be consistent & do the same thing for all night wakings.
Btw - he is such a gorgeous little boy. I love that pic
hth & let me know if you have any questions
Layla