I thought kobo touch wasn't supposed to upgrade past 2.5.2 after kobo took down 2.6.1 and replaced it with 2.6.1b, which wasn't meant for the touch. And I'm pretty sure that was before Aug. 12.
In any case, I think the issue with your SD card is that there is a bug that makes loading the SD card info from a shut off state take a long time. But it's not actually frozen. And it should only happen when you turn on from off
and possibly when you take out and put back in your SD card.
However, it is likely that it is not frozen and just needs a little patience to start up. It appears frozen because the little squares stop dancing, but in reality, it's still just working. The more books on the SD card, the worse.
The only work around I know is to keep it in sleep mode and only turn off when desperate. It should instantly turn on from sleep mode, if this is the same issue others and myself have described.
About the battery draining...do you have a cover? Does it have a pocket, or something else that could potentially touch the screen when you put your touch to sleep? That may be the issue. If you answer yes to that, you can try 1) put it to sleep 2) wait 20-30 seconds before closing the cover or putting it in its case.
If no, I'm not sure.