So I get the sense that the Volume II labs are beginning to run out of steam a little. This task regarding multicast distribution seems plain silly because you cannot configure R3 to selectively transmit 'every other' packet addressed to a multicast group out one dense-mode interface. Putting a tunnel in place to shield MCAST packets as they traverse R1 just means that the traffic is duplicated as it passes through R2 and over the tunnel. It is not load balanced in any sense.
Now. if there were two different Sources sending to the same group, then ip multicast multipath could be used to achieve per-spurce load balancing.
I wonder if the question and the solution for this task were supposed to reference two Sources located in Vlan 367?
Johnsg_uk