Don't know what to tell you about the creaking floor...you could probably, with a fair amount of labor, get under the trailer and shim them lightly at the cross braces. The floors in my house creak...its the nature of the beast.
The rock and roll? One chock on one side, or even a pair of chocks on one side isn't going to do it, that's even if you are putting the pair of chocks under the tires properly (most people just tap one under a tire and call it a day). Try a pair of BAL X-Chocks, one on each side. You are sitting on a set of rubber tires that give, on axles that are spring mounted and you are only supported at the four corners. The beams of the trailer flex (they are designed that way) and you will gain a great deal of stability by locking the tandem tires together so that they can't rock back and forth and they become much stiffer due to the pressure of the X-Chocks pressing into both of them. The only way you can get rid of 100% of it is to take the axles off, put the frame on a perimeter wall of cinder blocks...like a sticks and bricks.
My 2 cents, your mileage may vary...
2 Cats; J-Lo and Ragamuffin :R
2014 Thor Tuscany 40RX DP
2011 Ram 2500 Longhorn CTD HO
2011 Keystone Cougar 318SAB (now gone)
2008 FunFinder X 210WBS (Sadly gone)