4. I poll the rewards every 60 seconds, and if they drop such that profit gets below 115%, I limit the hashrate on NH to the minimum, and if it doesn't come up after 15 minutes, I remove the order. When it rises again to above 125%, I set the limit back up to my calculated maximum (see below).
So, basically, I would think that 3% nicehash mining fee, 1% buying fee, 2% pool fee and 5% delta (spilled hashrate) adds up to 11% potentially loss to cover for, so I think the 15% is a reasonable selling-threshold.
I ran this script for about a day, I think it picked up about 10 orders, and while I was hoping to make some profit, I only found out that I lost about half what I started with. Bollocks!
I forget what the actual amount is, but you all loose BTC when you cancel an order as well. How many did you cancel? I have a similar script, but you should also be adjusting your price to keep it on the lowest fringe. I have bots running that I haven't put BTC in the accounts in months, they continue to earn. Not huge earnings, it is tricky with NH. They have their ups and downs, but in the end they continue to grow.
I haven't really looked into the API in a long time but looks like that actual_last24h need to be /1000
the names are a bit messed up, I'll need to go look and see what they were actually mean to say. dev won't change them since other apps are now using them...