So you're saying that you only keep 100 grams and ditch the rest?
Yes, I only keep 100g that I fee. The rest is trash as otherwise it gets too big.
I work from that single jar only. Meaning when I do pizza, I only take what I need out of it to make the dough. Keep 100g of the jar, toss the extra and that's it.
I simply keep it on the counter top. Nothing else required.
The only back up is a little bit of starter in the fridge that I feed every 2 month or so.
Ultimately you will have to develop your own technique which is a combination of what others do.
I think I red 5 books and a dozen website about starter. None of them worked for me. Some people have special containment set-up with small heaters, ... many are too complicated and comber some.
My rule is if the starter is too weak to survive in normal environment then I let it die of natural causes.
As a side note, I also keep a vinegar mother and it is the same. I never dump any out but take what I need and randomly add left over wine to it. I have had this one for close to 15 years.