You might want to look at a thread started by G3750 who is building the PRR Panhandle Division. His aspirations are somewhat similar to yours. You might also give serious consideration to using track that will still be manufactured in a few years. Many here use Gargraves track (a lot of flex-track is used, but not by everyone) and Ross switches; some use Atlas track & switches; and many just use old fashioned tubular track and switches. These manufacturers tend to give you more flexibility in planning because they offer more switch and complex track variations.
Next, read some threads and books on track planning. I highly recommend Track Planning for Realistic Operations by John Armstrong (now on its 3rd edition). There are also many other fora devoted to model railroading, most of which have a section about planning a layout somewhere therein. Don't restrict yourself to O gauge or O scale because you will find great ideas in other scales.
Honestly, in my opinion only, you are trying to cram too much into the space you have for the time being. Better to scale down and start like John Allen did with a masterful 4x8 oval that eventually became the heart and soul of a much bigger layout.
Chuck
PS The trouble you report with Fastrack pieces not joining in a plan is a very common issue also dealt with in other threads here. Many have overcome that issue, but it's work that isn't necessary with other types of track. AND, Fastrack is very, very noisy.
