There are probably differing ways to achieve a working system, which is going to be the “best” or “easiest” is going to be harder to determine 
…
The drive containing you “old” home is “sdb1 ext4” with the UUID of “fe5dc2b2-5c93-463e-b882-f606e8395a9f” , yes?
How much user data do you have on that drive which you wish to retain, and do you have any means of backing that data up?