You’d either need different target servers with different operations (and chose among them with RouteRules inside your proxies) or use dynamic target url setting with JS for something like this.
The limit of 100 is 100 KVMs - ie, 100 maps containing both keys and values. Each KVM can have multiple entries (limit 5 million total across all KVMs per org) so I think a single KVM containing targets is probably what you want here, but I am concerned by “updating a kvm very frequently” - how frequently are we talking here? multiple times a second?