1. No need to disassemble it. A rag in salt water is enough to wipe it. Some people use a hand held brush to reach the inner parts. The only thing that needs to be cleaned well with vinegar/water solution is the pump. IT needs to be removed from the skimmer, taken apart and soaked in solution overnight. This needs to be done every 4-6 months to ensure performance and extended life.
2. Remove it and soak it or rinse it with RO or salt water.
3. It should be snug. I wonder if it is not installed correctly.
Here is a video on how to properly assemble, setup and install the CLSC-90HOB skimmer...
https://www.youtube.com/watch?v=NCdl4Xrw90s