This is normal. The frames you are referring to as floating are simply single frames vs. the other frames which are doubled. Keep in mind the futtocks are still bolted to the one below with chocks or scarphs just like all the others. Surely this is not as strong as a doubled frame, but it gives 2 advantages. Firstly lighter weight high in the ship where weight isn't desirable. Secondly the gaps between frames were meant to help keep the wood dry. Keep in mind these were still enormous pieces of wood in real life. Those frames will be more delicate when you are building the model, but you will find the assembly to be plenty strong once combined with the various wales, planking, etc. You can find lots of examples on build logs on the site including the various Swan class models.
I suspect the frames become cant frames starting at station 23, but I couldn't say with the information in the drawing.
I agree with mtaylor. You probably have more or less all of the tools you need to build one of the Model Expo kits if you have been building in plastic for a while. One thing I would add to the tool list if you don't have one is a pin vise and a set of small drills. Little files are also good to have. I build lots of plastic airplane models in addition to wood ship models. The biggest difference between plastic and most of the wood model kits is that you will have to do a bit more shaping, sanding, etc. on the wood models. A cool thing about the wood kits is you will most likely end up with a kit that is very unique and your own depending on how you finish, rig, etc.
