No you don't need to take it down to put in the SD card. You just need to unscrew 4 screws on the black part on the opposite side of the lens and install it.
If you want it to track longer, then make the make time longer than 15 seconds LOL. Make it 240 seconds. If the object goes out of view, it will then return "home" before the 240 seconds are up. By upping the tracking ratio, that is how you make the subject bigger, but the bigger the subject is in the frame, the more chance it has to lose tracking, so it is a balance.
You could fabricate or look around and find a pole that would extend it out to get past that big obstruction looking left.
I would really look at better waterproofing those connections.
For the snapshots, how would the camera know that it is fully zoomed in as that can constantly change as the object moves LOL. You could tell it to take more snapshots or use a VMS for further snapshots.