Go figure, it appears that caloric energy balance isn't the only factor.
A: Pre-Keto, odds are you we underestimating how many calories you were eating. Unless you were tracking every single thing you ate, there is a high probability you just didn't realize how many calories you were consuming.
B: It is super hard to over eat on Keto. It is possible, take lots of liquid calories in (heavy cream can do this easily!), and there are some other real screw ups, but eating 3000 calories of steak is pretty damn hard.
C: What you are reporting is common for people who have a lot of weight to lose. At some point it becomes a lot harder, at first you just have to sort of watch things, then you eventually do have to count calories. (Especially if you want a six pack, holy crap do you have to count calories!)
I'd also second that it's really hard to eat a massive amount of calories on keto. Water loss and perhaps some changes might make you leaner but most likely, over time, you're simply getting a lot less than, I dunno 3000 that isn't hard to do on a sugary diet.
Gaining muscle on keto /is/ hard. You can do it (/r/ketogains can help!) but wow you have to stuff yourself, which is sort of odd for Keto!
Also it's funny how the supplments folks are allowed to sell potassium. There's regulatory issues of having more than 99mg per pill (could damage stomachs or something). So these companies market compounds with potassium that aren't in bio-available forms.[1] "550mg!" people see, making them think they're all set (and hah, pulled one over on terrible government regulators). Nope. Same happens with magnesium. Seems rather misleading, even though they are printing the truth.
1: http://www.amazon.com/Nature-Made-Potassium-Gluconate-Tablet...
On the way out of her office I remembered I hadn't had any potassium for awhile, stopped by the grocery store, picked up some spinach, and a handful later (about a few minutes) the constant headache I'd had for a week straight went away.
So yeah, get your potassium in.
Made a vichyssoise the first time a few days ago (subbed most of the potato with cauliflower and parsnips) and have to say it was about the most filling soup I've ever eaten... had trouble eating the 2-cups I usually do for a "serving" of soup.
If going a more Paleo inspired route, fruit is probably the most easy to over do. I try to stay under a GL of 100/day, being diabetic it's risky for me to stay in keto too much, ketoacidosis is not fun at all.