Q1: What information is leaked by the electromagnetic emanations from computers?

This depends on the specific computer hardware. We have tested numerous laptop computers, and found the following:
In almost all machines, it is possible to tell, with sub-millisecond precision, whether the computer is idle or performing operations.
On many machines, it is moreover possible to distinguish different patterns of CPU operations and different programs.
Using GnuPG as our study case, we can, on some machines:
distinguish between the spectral signatures of different RSA secret keys (signing or decryption), and fully extract decryption keys, by measuring the laptop‘s electromagnetic emanations during decryption of a chosen ciphertext.