The squatting action is fairly normal for a goat in strange surroundings !!
Tie her up short when milking... you are going to get a waving hind leg that will probably end up in the bucket, this is quite normal at this stage !!!!!!!
If it is 1 leg in particular... usually is... then slip a soft rope around the leg just above the hoof and secure it out behind. Sounds awful but it isn't. I usually tie up the left hind leg because I milk on the left side.
The let down time is around 10 mins... you just going to have to persist, particularly the person who can milk... this may become a battle of wills, because leaving the milk is simply not an option. Mastitis will follow.
DO NOT be harsh with the udder... this can cause internal bruising, which in turn will make the goat even less likely to co-operate !! A firm massageing to bring the milk down from the top of the udder usually stimulates the release of milk.
This is one situation where the human must come out on top..... be herd leader.
The average BT will give around 1 gallon a day, after kidding., the milk figures you have been given at this time of year do sound rather on the low side.