You seem to be getting GW a bit mixed up.
The basic premise is centred around trust. Trust that you will always give enough reassurance to create no distress, then gradually reduce the level of reassurance needed.
We always put him down, say goodnight then leave to give him a chance to settle on his own, but to back as soon as he cries
That begins the whole process on the wrong foot. It begins with responding to distress (cry), not offering enough reassurance to create no distress.
This brings in the mistrust - will mumny/daddy go as soon as I start settling? If I don't cry mummy/daddy won't come back. So it creates a battle with deliberate staying awake and almost manufactured distress in order to guarantee the child reassurance.
GW starts with stopping that battle. Making the child know and trust that on every occassion you'll give all the reassurance needed. From this point it can be thought of as a series of steps.
Early in the process you may need to stay at a high step throughout. Then it will become where early into the bedtime you will start higher up the steps, progress up and down some steps in line with baby's distress, but always withdrawing down the steps when calm. Then as GW is more established you skip right to the end of GW, unless child is poorly, I'll or generally regressing and needs you more.
A chair isn't a good idea because it's static. It has a specific place. I would do it standing. An example of steps would be:
- standing by cot, hand on child's chest/back. Stay static. Maintain position until child is completely asleep. Sneek our once asleep.
- standing by the cot. Hand on chest if unsettled. Maintain position but withdraw hand when calm. Hand back if needed. Withdraw when calm. Maintain position until child is completely asleep. Sneek our once asleep.
- standing by the cot half turn facing away from child. Turn back and hand on chest if unsettled. Withdraw hand and turn when calm. Hand back if needed. Withdraw when calm. Maintain position until child is completely asleep. Sneek our once asleep.
- As above but facing door when calm. Go back and hand on chest if distressed, withdraw when calm.
- As above but step away from cot when calm. Always go back if distressed. Always withdraw when calm. Always stay from bedtime to being fully asleep, without denying the level of reassurance child needs at any time.
- As above 2 or 3 steps away from cot when calm. Stay there and wait until asleep. Go back and hand on chest if distressed, withdraw when calm.
- Settle in cot then wait stood in doorway when calm. Go back and hand on chest if distressed, withdraw when calm.
- Settle in cot then wait stood in doorway when calm. Create a mini-job. Something that will take 30s or less. "Just putting this towel in bathroom". Come straight back and wait by doorway. Go back and hand on chest if distressed, withdraw to doorway when calm.
- Repeat as above for a few nights so that popping away from door doesn't create any responce. Then pop away for a minute or two - but always come back and wait. Do several mini-jobs one after another. Always go back if distressed and even when calm.
- Settle in bed, leave door open, busy yourself upstairs until asleep. Back in room (and up the steps) if distressed, withdraw when calm. Close door once asleep.
- Settle in bed, explain you will close door while you stay upstairs but you will come if he calls for you. Wait right outside door initially because he may test you. Open door and confirm he is ok at any tiny tiny noise. The reclose door. Child needs to know/trust you are right there if needed.
I often have to go in and sleep on his floor
None of this would involve sleeping on the floor. That doesn't teach any withdrawal to independant sleeping.
Neither does any of this involve leaving, waiting for a cry and the returning. I think that is giving very mixed messages. Leaving and returning is more in-line with controlled crying than gradual withdrawal.