I don't understand how sending one glob of coins to one address actually sends it to or from multiple addresses?
Okay, so transactions consist of inputs and outputs. Say I want to send 10 BTC - I have two addresses in my wallet, one with a balance of 6 BTC and one with a balance of 9 BTC - Both balances will be used, to create a total input of 15 BTC. 10 BTC goes to the address that I'm sending to, and 5 BTC goes back to a 'change address', which is another address in my wallet which I control. (minus the transaction fee, which goes to the miners). This is why you see coins being sent to and from multiple addresses at once. It also makes it difficult to determine exactly which coins were sent where.
blockchain.info has a 'shared send' feature, which allows multiple users to combine inputs from their various addresses, and send to each of their desired output destinations. This makes it impossible to determine which input was destined for which output, effectively mixing the coins.
It looks to me like the thief may have been using this shared send feature to obscure the path of the coins through the blockchain. It is also quite likely that somewhere along the chain of shared transactions, somebody using the shared send feature may have been sending coins to SR, making it very likely that you would eventually end up at the seized coins address (which you did)
I'm afraid its very unlikely that the FBI, or anyone else, would have the time or resources to be tracking every transaction since the coins were stolen, especially for such a small amount (yes, 8 BTC is a lot of money to an individual, and I'm sorry for OP's loss, but in the grand scheme of things its pocket change. I imagine the cost of tracking it down would be much more than 8 BTC/$2500)