There are legions of people on this board that are more experienced than I, but my experience began in August and continues, in spite of a learning curve. These are my thoughts and takes based on the above.
I don’t consider the amount of water in the sourdough when working out the hydration, part of that assumption may be based on small batches but have not seen a significant difference between dough made with IDY and SD in terms of hydration.
There are sooo many people who say that consistency of timing of feeding and amounts of feeding are important. Listen to them! My usual “wing it” style does not work with consistency! I have “adopted the pet” and it has me on a schedule - to my benefit! I refresh my starter twice a day, once about 10:00 and again about 12 hour later. There have, obviously been times when that went sideways, or the fridge was used because I wasn’t going to be available, but other than that it is pretty close to full time.
I started with an Ischia culture, a gift from Arne, and available on line. After the initial feeding, backing up, an important step at the start I found, I now use 50 grams of existing starter, 50 grams of water and 50 grams of all purpose flour. And repeat and repeat . . . . .
Don’t expect it to be work or be consistent right away, it took me a month (or two or three . . . . ) to get somethings that was predictable in any way.
As said above, there are so many more experienced. Looking at their posts gives you an idea of amount of add as % and usually timing. The King Arthur website is very good for info and importantly how to dry a back up just in case!
It has been a fun but at time frustrating journey - enjoy!
My 2 fingers are complaining, so I will end there