1. If you mean the presence of only one instance of RDS, there should be no load balancing requirements in front of it. If you mean having more than one RDS instance, it also doesn't make much sense to load balance requests, because your database servers are likely to have different data for a given point in time. The only exception that I see in this rule is if you have only read-only RDS instances. In this case, you can probably take advantage of the presence of ELB (s) in front of them. If your application is write intensive, you should stick with a larger RDS instance or go to the noSQL database. Do not try to load DMBS read / write balance requests, because you will have to deal with synchronization and many other (non-trivial) aspects yourself.
2-, . -, . .