I agree with Roland and would just start from scratch.
Choose one node as the master, create all hosts and configure the remaining 8 nodes as satellites by using the node wizard.
And one thing that might be important when it comes to your boss’ expectations because you mention master/slave and master-satellites:
Master/Slave setup: There is no such thing in the Icinga2 universe compared to databases like MySQL for example. “Masters” are the “configuration master(s)”. If you have just a single node as master this node will always be the master. If you configure 2 nodes in the “master zone” Icinga2 will take care of the HA mechanisms and clustering and you should treat both nodes as master at any time.
(If you add a 3rd node to the zone -> everything will go BOOM! Seriously, don’t do it. A max of 2 nodes per cluster is what’s supported by Icinga).
And the actually important part is to steer your boss expectations and tell him that the setup you described means that you’ll end up with a single master, which is a SPOF. The connected satellites won’t (be able to) take over the service if the master node crashes. So I would recommend to add a 10th node to have HA and redundancy for the master.
All this and much more is also explained pretty well in the link @rsx shared above.