my milk flow is about same as yours. that time when i was about to return to work, my dear son had 6 feeds a day. one of the feeds i substitute with formula so i get to keep one extra feed of bf. after some feeds, if i still have strength, i will pump. so will pump out about 60ml more.
as to your questions
(1) i will freeze all my milk. to mix feed i will defrost in the fridge what i need. eg, if i have one packet 100ml and one packet 60ml and my baby only drink 120ml, i will defrost those 2 and poor out and warm out. dont't freeze back what you have defrosted. then the 40ml i will keep until the next feed and mix with a new packet from the freezer that i defrost. i will always try to find the exact amt to defrost. like if have 70ml and 50ml, exactly 120ml, i will defrost those 2 and finish up.
(2) i read that can be stored up to 48hrs in fridge and up to 6 months in freezer.
(3) it's better to first in first out. use up the earlier batches first. when you freeze immediately after expressing, most of the nutrients are retained and bacteria growth is reduced significantly. if you've already chilled the milk in the fridge, dont't freeze.
that's my expereince... hope it helps!