Smirnoff can you post a picture of what your forum looks like on your device? On my Galaxy I am getting the full page, however it is compressed to fit my screen. There is no mobile option turned on right now from what i can see. Just the variations of the large theme. Afaik with vBulletin 5 it is desinged this way to be a middle ground between full mobile and full site looks.
As for marking forums read, I have yet to find the mark read for all of the forums however if you click on the parent channel (the name in the header of each section) down at the bottom you can mark all channels within that section as read
EDIT: Check the top left under sections there is a mark channels read for me
The posting time has to do with the way vBulletin communicates with the server and how often information is pusbed back and forth between forum and host. Tweaking these settings is kind of hit and miss (it was for me anyway) it also affects the settings for how soon after you read a forum its marked as read with the different icon. Instant updates is very server intensive so the admins have to find a happy medium with the data rates