Absolutely yes. Turv, you weren't "overtraining" when you plateaued. You were totally under-eating. What did you weigh a year ago before you started lifting?
Nope. It's very possible to build strength without getting bigger. And it's possible to get "bigger" (weigh more) without getting stronger. Gaining strength without size is either due to training or nutrition (most likely nutrition). Gaining size without strength is almost always a nutrition issue.
Have you been gaining weight on your current 1,800 calories?
First, set some specific goals in order to develop a more appropriate plan.
Second, what are your current strength levels on the basic exercises - squat, bench, deadlift, row, overhead press, row, pulldown?
Third, when you say you have "enough ROM to do a reasonable squat", does that mean you can hold a good, deep third-world squat position for a full minute or so? If not, I'd make that the priority.