Reading everything you can get your hands on is a good start putting you and your kids first. Posting here is a good start. Knowing where Alanon meetings are is a good start too.
You're a good mom so make sure every decision you make continues to be in the best interest of your children. They can't make decisions for themselves that you can to feed them and keep them safe from your alcoholics poor choices to support his habits. The unfortunate thing about all of this is that their dad WILL put his addiction or addictions before you and them, so it's up to you to do the hard things. You're going to need all the support you can get from those who have been down the path you are on.
I understand how you want to confide in your sister, I've done the same thing, and like you, my sister has had a difficult time relating because she doesn't live with or raise children with an alcoholic. This is where this website and Alanon will be invaluable resources for you -- they ALL get it! Oh, and by the way, there is no such thing as a perfect marriage, not even your sisters...just wanted to get that out there.
I raised 4 sons with their alcoholic father. Its lonely and full of heartache. I pray you find the help you need much sooner than I did.
Hugs to you!!