1. The guest performance data will still be there as the names of the guest machine’s won’t be changing. The host performance data probably won’t be available as it should be tied to the old name.
2. No, the shouldn’t be any problem. VMware doesn’t use the data store name, it uses the physical address name which is different. The Data Store name is for us humans to read.
3. Put that NIC on a different subnet from your management network, and put the backup device on that same subnet. By default the traffic will go through the local network before it travels through a switched network.