1. HUF consists of all the coparcenors including their lineal descendants howsoever low. It does not matter that the karta or his son have their individual HUFs
2. Yes it is better to prepare a partition deed cum deed of family arrangement and register it
3. no need to take back the loan. It can be adjusted against the shares to be allotted to the borrower coparcenors
4. the amounts can either be equally distributed or there can be unequal distribution. It all depends on the mutual agreement between the parties. A partition deed indeed records mutual agreement between the parties, so it does not matter whether there is equal or unequal distribution. What matters is what the parties have mutually agreed among themselves
5. Ideally yes. Kindly consult your CA too
6. Nothing as such. Register the partition deed so that all are deemed to be aware about the actual situation and no party can take advantage on basis that he did not have knowledge about the partition having been effected in the family