I do not know the answers to your questions but I believe that they are not obscure points to those dealing with probate professionally
The fact that you ask them therefore implies to me that this is not an area you deal with. I am very wary of lay people “helping” their friends on legal /professional matters. Not a good idea for either party. I would suggest they seek professional advice to deal with the Estate and also get the trust properly set up in terms of registration, investment management, tax compliance etc. As I have said before, it costs a lot more to get things wrong than it does to get them right.
Seems to me you have fallen into the trap of assuming applying for probate is job done. There are a few tax issues here with ongoing requirements as part of the estate administration. Rental income, share divs etc all requiring tax to be paid by the estate at the relevant rate.
There is then constituting the trust, trust registration.all with other aspects of the estate administration.
The best way to help your friend is to suggest they instruct a professional.