Can not execute Findbugs: java.lang.OutOfMemoryError: Java heap space, while running mvn sonar:sonar -X
This is a well-known problem: Findbugs is really memory hungry, so I'm not surprised that with a 900MB project, you have to increase the JVM memory options quite a lot.
3 things you can do:
increase again the JVM memory options till it is OK
reduce the amount of activated Findbugs rules in your Sonar quality profile
refactor your project is smaller modules so that each module requires less memory to get analyzed by Findbugs
If I were you, I'd really go for at least option #3, because 900MB for a single project is really huge.