You probably took the R80.20SP version of the Maestro course which was quite outdated and lacking in detail. The R81.10 version of the Check Point Certified Maestro Expert course answers all your questions. I cannot post excerpts from the course material as I do not own the rights to do so. But to answer your specific queries in a general fashion:
1) In most cases Layer 4 distribution should be turned off in Maestro even though it is on by default. Layer 4 distribution will interfere with UserChecks and the Identity Awareness Captive Portal. There are some situations described in the courseware that will cause a dramatic imbalance between SGMs of the same Security Group if L4 distribution is disabled, and only in those cases should Layer 4 distribution be enabled.
2) IP routing has nothing to do with Maestro distribution. Maestro uses prediction to ensure that the information about connections is only sync'ed to the members that need it via a process called Hypersync; this avoids the 5 cluster member limit for the original ClusterXL Load Sharing. Basically in Maestro the original connection owner SGM determines where the forward path (c2s) for the connection would go as determined by the Maestro Hyperscale Orchestrator (MHO) if that SGM were to fail, and only syncs the connection to that one backup member. The connection owner also determines where the return path of traffic (s2c) will go as determined by the MHO, and syncs only that member with that connection. That subsequent member then determines which SGM would receive the s2c flow if it were to then fail, and only syncs that member.
3) cphaprob corr will show you correction statistics. The correction process is quite efficient, and even a correction rate of up to 100% is not necessarily cause for concern, as the correction rate is heavily influenced by the presence of NAT and VPNs.
The R81.10 version of the CCME exam has been updated to sync with the new courseware, it is possible you took the R81.10 version of the exam after attending the R80.20SP version of the course which would be a problem as the R81.10 version of CCME was heavily revamped.
Gateway Performance Optimization R81.20 Course
now available at maxpowerfirewalls.com