If you’re running 32bit Java then you won’t be able to bump the maximum java heap size up in the ignition.conf file to much more than 1500MB. Attempting to do so will likely result in your gateway not being able to start. You could however run 64bit Java and 64bit Ignition which do not impose a limit on the the amount of memory you can allocate for the Java heap space. That being said I’ll get some further clarification on whether or not this issue is indeed being caused by a lack of memory and what the necessary fix would be.
As for the issues regarding starting up of the master node in your redundant system, what exactly do you mean by the master not starting up correctly? Does the gateway page never become available? Does the connection status on the backup machine say that it’s connected to the maser node?