Wallet not updating with balance and database error

I'm fairly new to using bitcoins and have been having some trouble with my wallet. I bought bitcoins on coinbase and transferred them to my bitcoin core wallet. The transaction was confirmed with 616 confirmations, but it has been several days and the balance has not shown up in my wallet. At the time, the wallet was was synchronizing with the network for what must have been a total of 24+ hours and was less than half way there. Last night, before it was done synchronizing, I got a database error and now it's "Reindexing blocks on disk" and is 3 years behind. Are my bitcoins lost or will they be visible in my wallet once my wallet is done reindexing?

Can I exchange BTC from CoinBase?

I have read the articles in the BitCoin website and I thought of implementing the BitCoin payment method in my website.

I registered at a payment processor website called "CoinBase". Unfortunately my country is not supported for the Buy & Sell feature.
I am thinking of accepting payments and later using some sort of exchange website to cash out. If I do start accepting BTC should I store them in the CoinBase wallet or use something like BitCoin Core? I am asking this because I heard that some BitCoin services steal the BitCoins from their customers and run off. Other than that, storing them online is probably more comfortable.
Could I get some suggestions on good exchange websites?

Thanks in advanced.

How should one manage the Bitcoin blockchain on a Linux laptop with limited storage?

I want to run Bitcoin-Qt on a laptop that has limited storage (it has an SSD and is used for many purposes that all require a bit of hard drive space). Assuming these hardware limitations, what would be a good way to manage the blockchain?

So, to be clear, I cannot store the blockchain on the laptop and I want to be able to make regular transactions portably on the laptop.

Has anyone proposed a human only proof of work system?

There have been suggestions of proof of work requirements that exclude GPUs or ASICS (or try to) but I was wondering if anyone had suggested a proof of work that is not suited to being solved by computer at all, so that the miners would be humans working on proving their own work done - work that cannot (currently) be performed by a computer in a competitive amount of time.

This would presumably need to be quickly verifiable by computer, but not independently solvable by computer.

If this hasn't yet been proposed, is there any apparent reason this would not work?

What's the maximum possible utxo growth rate now? Can that be turned into an attack?

Now bitcoin unspent transaction output growth rate (not total size) can be, 260k utxo/day (3×60×60×24). With 8MB blocks, that's 2.8 million.

Single 1 bitcoin output can be split into 1000 x 1 mBTC outputs, within 100 minutes (10 blocks). Then, those 1000 outputs can be moved individually, as required..

Does this kind of utxo bloat attack work? Anything wrong with my calculations?

In what scenarios can the blockchain size decrease for bitcoin?

I am running a private bitcoin network for which I changed the target time between two blocks to 12 seconds and the difficulty adjustment to 25 blocks interval. I ran the network for about 4 hours with 50 nodes. In one of the node's logs I observed that the blockchain height increased up to a maximum of 181 and then started decreasing, all the way to 38. what could be an explanation for such a strange behaviour.

Please refer to the log below:

2015-11-04 01:58:47 receive version message: /Satoshi:0.11.99/: version 70011, blocks=181, us=0.0.0.0:0, peer=2, peeraddr=127.0.0.1:44117
2015-11-04 01:58:47 UpdateTip: new best=0000005265ca4ce01ad0d06f45cf475bf303de3d64e942c5cf1177e00f346c78  height=180  log2_work=37.083283  tx=30941  date=2015-11-04 01:53:17 progress=1.000000  cache=0.0MiB(1tx)
2015-11-04 01:58:47 UpdateTip: new best=00000052a34cedf3c5ddbeb46d36644654523db855c4cce984d2623e840dd219  height=179  log2_work=37.082953  tx=30940  date=2015-11-04 01:53:10 progress=1.000000  cache=0.0MiB(2tx)
2015-11-04 01:58:47 UpdateTip: new best=00000030fd7652affb883f05fe0c98e7fe3fbc3cfd74808e061ed05ec61c22e6  height=178  log2_work=37.082623  tx=30939  date=2015-11-04 01:52:55 progress=1.000000  cache=0.0MiB(3tx)
2015-11-04 01:58:47 AddToWallet c32bcbd8102c602a5e71ee717232e204435f331dce6fbfb9eb5d552698faa95b
2015-11-04 01:58:47 AddToWallet 1c91517aeadd12bcbcfdf4a1423b671d405543ae9abfbd87078969ce1971663f
2015-11-04 01:58:47 AddToWallet b11f9c2e3b1ab3d3983da63783bb95903d89405243d0716ea88272a9261b7a33