Just choose walking. Does it really matter that much? You can always change the activity name to reflect that it's on a treadmill.
I want it to count as walking miles and as a treadmill activity just like "treadmill running" counts towards running miles and as a treadmill activity. Right now there is an option for treadmill running…
Are you saying that calibration is not automatic from that
I do not know how it works with Foot Pod, I only know how it works with my HRM-Pro - the calibration is automatic and continuous, but I can reset and start it anew, and I can also disable and pause it - for example when I am happy with the calibration, and do not want that the next run (or walk) under worse conditions skews it.
my watch connected to GPS 30 minutes in anyway. Is there a way to manually disable that for when I'm inside?
Yes, in the settings of the Walk activity. Better is creating a copy of it - one with GPS, and another without it.