As to milk first or last in the main the tea bag and non use of the tea pot has resulted in milk last or the tea does not brew. Yes I use a tea pot, one of the double Turkish types with water in bottom pot and tea in top one, always made strong, and diluted to taste when poured. The induction hob can keep the tea warm well past the point when it is stewed. And since I don't take milk in tea then it really does not bother me. Pouring tea has never broke a glass yet.
In work canteens there was always some one who would go OTT with milk or sugar, the sugar was not really a problem, but the milk was, in the afternoon tea break we did not want to go out and buy a fresh bottle. So milk went into the tea pot. In Falklands also the sugar you had tea NATO that was fixed amount of milk or sugar if you didn't like it tough.
As to cost of boiling kettle and storing milk it is hard to work out. I have often gone down stairs to make coffee only to be distracted so kettle boiled but nothing made, and with the fridge the time this is all worked out is when you buy the fridge/freezer. You decide how big and once bought you can't shrink or expand it to fit less or more. However my wife tries all she does is break yet another draw.
Keeping fridge/freezer full or half full is always a good debate. Full and it is more likely to survive a short power cut, half full you loose less with a long power cut, half full the air circulates better so less likely to get hot spots, but good draw design should look after that anyway. With half full you loose more cold air when the door is opened but full it takes longer to find food so door is open longer.
I did try to measure how much power they use, but the readings were up and down like a yo-yo just too many variables. As to milk big problem for me is shops offering two for a lower price, so I look in fridge and short of milk, I buy one, on returning home I find wife has bought two so need to use it up fast before it goes off.
Years ago we got daily milk delivered, then it went to bi-daily deliveries and after 3 days we were finding the milk had gone off. The milk delivered was same as in super market yet milk from super market would last a week. Hence why we stopped getting milk delivered plus they were regularly getting the order wrong and leaving too much or too little.
Milk on the Falklands to Stanley used the plastic bag and special jug. In Mount Pleasant we could not buy fresh milk. The system seemed to work, but there was no other fresh milk, so it was plastic bag or nothing. But in UK we have fridges designed to take milk in the door so unless the package fits in the door forget it, it's a non starter.