I can help with the questions if you like.
You don't need HDWriter. Its only two vaguely useful features is that it can join clips without re-encoding and it has a videoplayer which some use. It has a hopeless UI. I do not have any compatibility issues on 64bit system.
The TM700 is recognised by W7 as an external disc. If you plug in the USB you can see the two storage areas (Card and Internal Memory) as a removable disc in windows explorer. You can simply navigate to the "stream" folder and drag and drop the files to your PC. The files are numbered 00000.MTS etc. The MTS is common extension for video camera. They are .h264 in a mpeg transport stream container. They are the same as a .m2ts file. You can use them directly in PD9.
Bluray spec do not support 1080p60 but only 1080i60 or 720p60 (plus others). DVD, as you know, is 480i. Perhaps consider burning your projects to AVCHD disc on DVD which any DVD burner can do and which can be played in many Bluray disc players. There is some advantage to shooting on 1080p60. My advice would be to shoot in 1080p60, edit and then produce three versions: one in 1080p60 for storing/later use, one in 1080i60 for AVCHD disc and one in 480i for DVD.
My PC is nowhere near as well "spec"ed as yours and I work with the files fine.
Long files are split but not as short as 5 mins. I will check for you today. I wonder if HDWriter joins the clips if I use that to transfer to PC?
Hope all this helps.
ps the TM700
is impressive
Panasonic SD9, Panasonic TM700, Panasonic SD600, GoPro HD Hero.