When to freeze breastmilk ?

Hi all, I would like to know the sequence on when should I freeze my breastmilk. Currently, I have excess of 400ml to 500ml of bm per day based on my 2 months LO intake. I will put in fridge fresh for 2 to 4 days. Sometimes it will start to have abit of sour smell after 2 days then I will have to throw it away. Maybe my fridge temp not right previously as I just moved the bm to chiller compartment 2 days ago. So my question is should I freeze my bm every pump or freeze partial portion and the rest put in chiller for next feeding? Also, when should I start using my frozen bm? Is it after I stop pumping bm ? I have been storing my pumped bm in a storage bag and pour for 2 to 3 feedings. Not sure is this the right method or should I store by a fixed quantity (eg 100ml). My LO refuse to latch since day 1 so I can only pump and store for feeding. Appreciate your kind advice. Thank you