Hi Tony,
Hi all,
I'm new to this forum. My first post.
This is a most unfortunate start to your first attempt at all grain. The boiler is going to be a problem and the mash temperature is too high. I would suggest you get an insulated cooler box standard size, whatever you use to take your beer and sandwiches camping with you. Use this as your mash tun. As you're brewing in a bag you don't need a tap and straining system. Use your boiler to heat the water. Boil a kettle and throw the water in the cooler box to pre heat it. Raise the water (about 3 gallons) in the boiler to 72C. Throw away the pre-heating water and pour the water into the cooler box and stir in the grain. Stir well. MASH it! It should settle out at about 64-66C. Don't worry if it's a bit less than this. Put the lid on. Put the kettle on again. After 10-15 minutes check the temperature of the mash and raise it to 65-66C with boiling water and stir well. MASH it! Put the lid back on. I leave my grain in the mash tun for 90 minutes. Half an hour or so before the end off the mash, put a couple more gallons of water in your boiler and raise it to about 75-80C no hotter. This is your rinse (sparge) water. Transfer to another vessel as you'll need your boiler empty to receive the wort from your mash. When you've drained the wort into the boiler, drop the bag back into the cooler box and flood the contents with the sparge water. Add to your boiler and continue until you have the full quantity you want to boil. Proceed with the rest of your recipe.
Sorry for the detail, but you said this was your first time and I'd hate for you to be put off on your first attempt.
Good luck.