So very sad to read this Joyce - yes sometimes this can be very effective especially if it co-incides with an adjustment in medication which works more effectively.
I personally would not want to be repeating the abdominal taps more than a few times - I understand it is not a comfortable procedure
However only you can make that decision - it depends on how Sydney is reacting to the procedure.
How is he in himself?
You are doing a fantastic job of caring for Sydney - he is lucky to have such a wonderful guardian, it sounds though like it might be time to start thinking seriously:
I would write down the things that you think are important to Sydney to give him a good quality of life
These would be on my list:
managing a short walk - even if it's only 5 minutes for the stimulation
Being able to eat and wanting to eat [2 different things]
Able to move about happily
Do you have water bowls near him at all times? [sure you do but just checking]
Managing a cuddle or whatever affection he wants
Being able to breathe when lying down
Not in any distress
Most importantly obviously - is Sydney still enjoying life?
Mine have always let me know in some way or other that things are coming to an end - and once you've made that decision, there is an air of peace about them even if they are in pain. I think there is also a calmness within you that the decision is made, even though it's not the one you would like.
Yes in some ways we'd like them to go naturally - but actually going naturally can be extremely unpleasant for them, and a huge shock to us to find them suddenly gone. Sometimes it is nice - one of very few I heard of was the lady sitting in her garden with the Cavalier at her feet, and he just passed away peacefully - she bent down to fuss him and he'd gone - but that is SO rare.
So I've always felt it is better to go too soon, they don't suffer at all that way. Too many are left too long and that is just cruel and you feel guilty forever.
I always have the vet out to the house, put the other dogs away - have something very special for a treat - such as prawns or sausages - and have them lie across my lap on a towel and feed them the treat whilst the vet lets them go. This way it has always been peaceful. You can have time to say goodbye - and I always let the others say goodbye too so they don't look for them [will still grieve but not search which can be distressing]. I'm not sure if you have any other animals in the house.