That is very disappointing.
If we look at it from another perspective, it's actually good news because if we can't solve this puzzle even with the clues, imagine how safe our Bitcoins are from brute force cracking
Well... maybe they're not THAT safe (if we get clues If we look at it from another perspective, it's actually good news because if we can't solve this puzzle even with the clues, imagine how safe our Bitcoins are from brute force cracking
)... So at around 1509 hrs UTC on 28th September (around 0409 hrs on the 29th local)... my script spat out another possible hit... I was working a night shift and so I didn't actually get around to checking it until around 8 hours later.
Amongst the 3 new possible hits that had been generated, one started with "1qk...."... could this be it?? I quickly checked on blockchain.info... "Final Balance: 0.5001 BTC"... WOOOOHOOOO!!!!!!!
So I quickly imported the private key into my wallet and transferred my newfound loot into my own personal address. 
The private key turned out to be: 5JKPapJwgyEij3sxYRAEnixyiFgxqkVhgZXv9bWWknBexegx6tM
[redacted]
Analysis after finding the key shows that in addition to my (thankfully correct) assumptions on upper/lower case, that black tiles were all uppercase, while the red and darker green tiles were all lowercase.
In the end, the script only got through just over 1,103,000,000 keys (in just under 12 hours) before I got lucky:
Quote
Checking [8589934592] Keys...
Start: 2016-09-28 17:08:17.702438
1000000 Addresses 2016-09-28 17:08:53.797499
2000000 Addresses 2016-09-28 17:09:30.093016
3000000 Addresses 2016-09-28 17:10:06.433803
.
.
.
1103000000 Addresses 2016-09-29 04:09:38.866786
We have a possible winner!: 5JKPapJwgyEij3sxYRAEnixyiFgxqkVhgZXv9bWWknBexegx6tM
1104000000 Addresses 2016-09-29 04:10:14.934280
.
.
Start: 2016-09-28 17:08:17.702438
1000000 Addresses 2016-09-28 17:08:53.797499
2000000 Addresses 2016-09-28 17:09:30.093016
3000000 Addresses 2016-09-28 17:10:06.433803
.
.
.
1103000000 Addresses 2016-09-29 04:09:38.866786
We have a possible winner!: 5JKPapJwgyEij3sxYRAEnixyiFgxqkVhgZXv9bWWknBexegx6tM
1104000000 Addresses 2016-09-29 04:10:14.934280
.
.
I sent a note to the puzzle creator to let them know... and I have created a PasteBin with my source code in case anyone wants to see my pretty ugly and untidy python code
I didn't think anyone was ever going to solve the puzzle. Perseverance was the real key
Congratulations!