(sorry if this comes off as a bit blunt; I do not intend it to be) I also use just my forge to HT, and the temp gun is great for this style of HT. 

the others gave great advice, but I am wondering what kind of oil are you using? 80CRV2 can be hardened in a high-speed oil park 50, but there is a greater risk of 80CRV2 cracking in this oil. It's better to use something like AAA quench oil. I brought it up because The break looks remarkably similar to a stress crack I have seen in some blades. Parks AAA does require preheating use; however, you can use a large crockpot to hold and heat the oil. I use a lower-end one and just set it to warm. but I think higher-end ones that you can set the temperature to or come with a digital thermometer that you can dip in.

I can see your tip has a bit of blue close to the edge, and that blue has travels close to the edge. Wet sand, a backing sheet, and water is a great way to do blue backing. 

Also, I suggest picking up a copy of Kevin Cashen's Heat treatment video from the store. It is worth the price, and he gives great advice on how to Heat treat in a forge in it. also, I suggest using simpler steels like 1080, 1084, 1095, and 1075 for now as they are a bit easier to Heat treat in a forge than the more complex steels like 80CRV2 as 80CRV2 is a bit trickier to heat treatment in a forge.

I hope this helps and keep up the great work

I use a european quench oil (Rye oil is the manufacturer) it is equivalent to AAA oil as far as I know, I also preheat it using old deep fryer elements.

I have now installed a thermocouple on my forge and found out that my temperatures were way too hot. New tests at the correct quenching temperature solved the issue, and I have great performance now.

I guess I was just taking heat treat a bit too simple and needed to actually check my temperatures and focus on the fase changes better.

Oh, and on the test knife the spine blueing did indeed get a bit out of control, normally I use a bread tin full of water to keep the edge cool.