1. I have read your post, and I have experienced the scud battery for about a week now, so I will see how I can advice you. Firstly, there are 2 main options for you IMHO.

The first is to buy 2 scud batterys and keep 1 charged with you as a spare for when the first one dies out on you. You might want to consider an external charger for when you want to charge 2 empty batts faster. Note that the scud battery has approx. 15 percent more juice, so you can make your own calculations based on the standard BL5J, possibly considering the age of the battery. Seeing your usage, 2 scuds will probably handle it.

The second is to make a dual (scud) battery mod as read in this thread multiple times, with the mugen battery cover to seal those in properly. This adds some bulk, but no need for swapping. You know the (dis)advantages of each one I persume.

2. Not that I know of, cause if there was one, one'd have probably been found by an forum member here and have been discussed in one of the battery threads. The mugen is probably better than any selfmade thicker cover.

Cheers.