What is the point of this? Your wanting to load share to 2 different vpn connections off the same physical interface? And the same TUN interface as well?

Have no clue to what is the use case here... What is the point of the complexity - what does it get you? Your worried that r44 or r45 go down? What is the point of the loadsharing across the connection..

NHRP - with just the 2 connections.. With GRE and IPsec involved as well??

Is this some sort of class work - seems like nonsense waste of time, I see no real world application here. And down the rabbit hole we go...

Probably not in this case.