Hi Justin,
many questions, but I feel your urge to know all the answers to feel assured and more energetic to start with this big project you have....;-)
I will start by assuring you that SME still does what you described and indeed creates a task which calls the SME powershell module and executes the backup/snapvault.
Howegver, with 7 mode 8.2.3 (I assume you have that since you talked about SnapVault license), you do need DFM protection manager and integrate that with SME,SMSQL or SMSP;
else it will be more tricky to get snapvault and Snapmanagers working with handmade/Professional Service scripts...
When you say you are using NFS only, you mean vmware datastores made of NEtApp NFS shares? If so, it's no problem. you can use RDM lun's for all products you mentioned.
You can also easily setup iscsi in ESX and on Storage system, that's really more simple than you can imagine and it would not cost you 64k, rather 64$ for a couple of IP's may be 😉
regarding your last question, "Does anybody know if NetApp would consider 'taking SnapManager back' and replacing it with SnapProtect?" I think you should have a friendly chat with your Netapp or Partner Sales rep. If you ask me, I would stick to either one of them, because after having taken the burden to setup either one type of solution or the other, I would not throw away the whole config and start all over with the other. I guess that's just me.
hope it helps,
Domenico.