Well, damn. I hope someone can get you everything you need to know and I hope you can do it! It is an incredible thing to see. Very humbling knowing how destructive and deadly that volcano actually is.

I would personally just hold back until the observatory is open. You'll get a better experience then, you're way more likely to get nice weather, and you shouldn't have any access issues.

Otherwise, wish I could tell you more about what you asked, but I have only ever gone in the summer.