making my first cider tomorrow, please review my process

Here is what I did on my first cider
Sanitized 5 gal Carboy blowoff and bung

19 quarts 100% apple juice
700g honey
10oz brown sugar
18oz turbinado sugar
16oz pure cane sugar
Lalvin 71b-1122 yeast

Poured nealy all apple juice in Carboy
Put all sugars and honey in pot and gently heated with about 1/2 quart of apple juice to help dissolve
Added to Carboy and stirred well for about ten minutes
Pitched yeast. And put on blow off hose

Og 1.078

Was unsure if I needed a blowoff because this is the first time I hAve messed with wine yeast. I filled the 5 gallon Carboy about an inch past the 5 gal mark so I don't have much headspace at all.

From what I read this doesn't produce much krausen so I hope Half my batch doesn't end up in the blowoff container

Most would suggest not boiling/caramelizing the honey, as it ruins a lot of the natural favors in the stuff. Plus, baddies will not grow in honey. The sugar content is far too high for anything to grow in it. That's why you hear stories of people coming across jugs of honey in ancient tombs that are still perfectly edible.

I've also heard people say brown sugar gives odd flavors to beers/ciders, but I still add a cup or so per gallon to my version of Edwort's apfelwein.

Also, make sure the cider is without preservatives. Just juice and vitamin C.

We are good on the apple juice. As far as not cooking honey. Do I have to pasteurize this if I don't heat everything up?

You will probably want to pasteurize eventually to stop fermentation, depending on what style of cider you want.

So if I want a sweeter cider. Bottle after 4-6 weeks. Pasteurize after 3 weeks in the bottle?

Montrachet is a champagne yeast, so it will dry your cider out pretty quickly. If you want a sweeter cider, I would suggest letting it do so, then allowing your cider to clear in primary or secondary for a while (maybe a couple weeks to a month), then back-sweeten and prime with sugar and apple juice, bottle and pasteurize as soon as carbonation reaches the level you want. To simply say "pasteurize after 3 weeks" means you will have a basement full of shrapnel and sticky appley mess.

Edited steps in op