Are you saying that if I obtained my BTSX from an exchange the exchange obtained them from one or more of the original investors?
Yes.
Q5: Interesting, I don't recall ever seeing this mentioned, is it in the wiki somewhere? I looked at the bitsharesblocks.com site which lists a total supply of 1,999,902,838 and unclaimed of 662,319,002. The difference is 1,337,583,836. Why is the total supply such an odd number?
Initial distribution was 2B distributed 50%/50% to PTS/AGS holders. Some of the trx fees paid are destroyed which results in lower than 2B total supply.
This uncovers yet another gap in my understanding, that being how BTSX (or any type of blockchain "coin|share|note|thingy..." are created in the first place. Are you saying the genesis block "defines" the total number of outstanding shares and who owns them, and in the case of BTSX the genesis block lists all of the account keys for the PTS and AGS investors that existed when the genesis block started the BTSX blockchain? But the code is what allows for diluting, which just means increasing the maximum niumber of shates|coins|etc, right?
Yes. Dilution is not yet enabled. There are some ongoing discussions about that.
If a "block" is a group of transactions, what transactions make up the genesis block if it is purely a definition of the total pool of BTSX and the account keys of the owners of the BTSX in that pool?
There are no transactions in genesis block. Just a list of keys and balances.
Q8a: what ndo you mean by "unspent outputs"?
Any transaction moves BTSX from one address to another. Unspent output is a BTSX amount that is not included as input to any transaction included in blockchain.
(Transaction has input(s) and output (and change address)).
Basically this is the BTSX anyone has received but hasn't spent. All unspent outputs combined equal total supply (assuming no bugs).