Breaking Bread in Nor Cal

Greeting from Northern California.

Just a tad about me.  Name is Jay.  I teach homebrewing and sell home brewing supplies for a living.  I recently built a Pizza oven out of a used 1/2 BBL keg and in the process I was discussing pizza dough recipes with customers.  I have a customer that gifted me a 20 year old sourdough starter and so the bread venture began.  I started reading about sourdough pizza dough but quickly dove down the rabbit hole of sourdough bread.  

So it begins.  7 days ago I started feeding my new pet.  I am calling her Demeter :)  

After about 3-4 days of feeding her I decided to try my hand at a sourdough dough mix.  Watching a few YouTube videos I came across a guy in Ireland that has a lot of really cool easy to follow videos and I dove in!  

Here is the recipe 

800G bread flour

460 ML water

12 G salt

320 ML starter

Mix and kneed till window test proves good then into a clean bowl for about 3 hours to proof.

knock it down and portion and into the proofing baskets for 3-4 hours

Pull from baskets and into a 425*F oven for 30-35 min with a bit of steam

For the most part I am getting an OK bread.  "for the most part"  I am having my dough collapse when I cut it before I put in the oven.  

Does anyone have any insight in this?  Too wet?  To dry?  Not enough proofing time?  Too much proofing time?  I am a little frustrated but I am dredging forward and thought I would ask a group for a little help and insight.

I will be starting a new thread on my journey, issues and all.

Thanks for any insight!  

Cheers

Jay