I have the exact same problem. The only difference is, I got it to start one time by removing the battery and all cards, for 10 minutes, then turning it on with just the battery. Haven't been able to get it on since. (The battery died and now it won't start up again) stuck on the dots forever.

When you plug it in from off does the phone go into a reboot loop? Mine does...or when you power off the phone from the 5 dots screen does the phone make a low tone as it switches off? Its not the low battery sound..

I think my phone memory is corrupt or something cos when I plugged it in to PC when it did boot I got all sorts of errors

I also bought my phone form US so bad news for warranty. Any other updates on this?

Edit: Oh and yes I also flashed Emmc, enabled R&D mode and did everything else that you did