Sourdough Attempt V and Final, really

I remember seeing the sourdough recipe in my bread book using milk, so I thought I would give it a try with some off milk.

I mostly follow the recipe in making the "starter", left it to fester for three days and developed some noticeable bubbles, I proceeded in making the bread.  I following all the kneading instruction, kneading a very wet dough for a long time, my arm ache the following day, forming the dough by folding and letting it rise for over 6 hours.

I used the casserole dish as my base, the bread came out with a little bit of air bubbles, still very dense.  It was edible.  I am not sure what I have don't wrong, I suspect I should have let it rise for another few days?