
Hi
There ar elots of other things you can try rather tahn an anti bark collar
It sounds like he wants company and has trained you all well to come when he barks.
I have had this in the past with my own GSD who I sadly no longer have and with some short term fosters when I was unsure I could face having a permenant dog again so I know what it is like and when you are tired from weeks of it exhaustion kicks in and you feel so much worse.
You have established a routine and simply put you need to establish a new one- Sounds easy and can be but may take a few weeks as the existing routine probably did too without you noticing it creeping up.
This is just what I would try - I am not an expert though.
Get up and let him out to relieve himself- do not pet him and try not to speak to him- I am ssuming he uses the garden immediately rather than waiting on a walk?
Bring him in and confine him in one room with you (so he cannot reach the stairs to bark up)
Perhaps put his breakfast down or put him back to bed with a favourite toy (ideal if you have a crate because he will not run around)
Next is a cup of coffee/tea and a magazine or paper which you should do whilst ignoring him- The aim is to provide him with the company but be as boring as possible
You would probably do this for a few days- gradually getting up and leaving the room for short periods even if just 30 seconds and building up.
Ignore any barking and importantly ignore him being quiet too - By priasing when you return you are increasing the excitement - It's no big deal you come and go as you like and shouldn't need to praise.
The aim is to get him that he can go to the toilet and then either go back to bed or amuse himself without you whilst you go about your morning routine.
Might want to consider if maybe he has lots of left over energy if he needs more exercise on his walks- maybe take a ball or go with other dogs so he gets a good run around and so is not so full of life in the am. Also if he knows his morning walk is coming at a set part of the routine that helps too.
As I say just some suggestions that have worked for me but maybe something of use.
Good luck