1) A spark when connecting the battery cable is not a sign of "battery drain", it is indicative of modules powering up and capacitive charging of items in the system.
2) If you think there is too much current flowing when the car sits, disconnect the battery ground cable and insert an ammeter and DIRECTLY MEASURE the current.
Now, there are some things you must know about how to make this measurement.
a) When you restore the connection, various modules will "wake up" and current flow will be as much as .5 to 1.5 amps. THIS IS TEMPORARY, keep the connection intact and wait THREE MINUTES, after this wait, the current you see is real and is the long-term value you are looking for.
b) If you don't wait, as in a) above, you will ALWAYS see current draw and you will chase your tail for days.
c) The Amp Hound is a good start, but when you want to know EXACTLY what current flow you have, you MUST break the ground cable connection and insert an actual ammeter. The Amp Hound is measuring voltage drop across the slight resistance of the fuse and interpreting what the current is, but this is an approximate measurement. To prove what I say, use BOTH the Amp Hound and ammeter at the same time - you will see how far off the Amp Hound's readings are.
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Attached is a PDF I wrote that addresses the Crossfire-specific aspects of "finding battery drain". It could use some proofreading, please excuse the fact that it is not well written.