first all grain, way over recipe sg

First off thanks, without the info i got from this place I'd have a lot more issues with my first all grain batch than I do.
Two questions (I did use the search engine but no luck)

First I brewed the midwest oatmeal stout which has an sg of 1.046. My wort is 1.070. I threw the priming sugar in the boil so as not to waste it and I added a pound of lactose and an extra 12 oz. of specialty grain to the recipe. How did this get so high? and is one wyeast activator going to be enough to ferment this thing?

Second I'm a total noob and I over chilled my wort to 58 degrees, panicked, and pitched my yeast anyway..... Any adverse effects from that?

Your OG is high because you added priming sugar, lactose and additional grain to the recipe.

Now keep in mind that if the lactose was not part of the original recipe your FG will be different as well, probably on the higher side

The yeast will work but you are really under pitching. If you plan on continuing to use liquid yeast learn how to make starters and consult in line calculators to figure out the required pitching rate

You added a bunch of extra ingredients and wonder why your OG was off? Of course it is going to be higher because you added a couple of pounds of extra ingredients. It will also probably finish much higher because of the extra pound of lactose.

My experience level is pretty low, seemed like a huge change for a little sugar. Got a lot of learning to do, thanks guys!

That's what it's all about .. Live and learn , on the flip side you might have just brew your most epic brew .....! Mean while let work for you , and always remember don't worry relax and have a home brew .....

And cheer on your imperial Lactose oatmeal experiment !