Questions about safety and reversibility of SD card partitioning.
Basically your approach is sound, with some minor adjustments I'd suggest:


You could do that. But it would be easier to simply shrink the existing partition. Using the right tools, that would even keep the data.
Of course you can, but you'd lose the data from one of the partitions: Simply remove one partition, and resize the remaining one to fill the entire card. But do NOT use NTFS :) It must be FAT then again, as it was before partitioning.
Depends on your device/ROM. If /extSdcard was, before repartitioning, the place you found the external card, after repartitioning you should find the first partition there. If not, simply use a terminal app (or adb shell) and issue the command mount (or, possibly easier, df) to list all mounted partitions and find where it went to. Should be the only one using FAT, so easy to tell ;)
That "strange path" points to your internal SD card. In case you wonder what then /sdcard is pointing to: to /storage/sdcard0/ (it's a so-called symlink).