Hello, welcome to the forum 
As to #3, the increase in world size is caused by the compression factor, we decided to try it out because it should be much less CPU-intensive, so the Pi won't have to do so much compressing and could spend its time on more gameplay. The damaged world is most likely a result of the chunk generator kicking in for some of the chunks. Did you change your generator settings? That's the only explanation I can give for different terrain being generated. If you make a copy of the old setup and issue a /regen command somewhere does the chunk get reset to ocean, too?
As to #3, the increase in world size is caused by the compression factor, we decided to try it out because it should be much less CPU-intensive, so the Pi won't have to do so much compressing and could spend its time on more gameplay. The damaged world is most likely a result of the chunk generator kicking in for some of the chunks. Did you change your generator settings? That's the only explanation I can give for different terrain being generated. If you make a copy of the old setup and issue a /regen command somewhere does the chunk get reset to ocean, too?