To answer your final question: no. Every calculator is useful as a guide, but there are so many variables to the individual that none of them are reliable. There are some very convoluted formulas out there, then there are much simpler ones, such as: take your bodyweight in pounds and multiply by 10-12 (so, in your case, 2,600-3,120kcal/day) for weight lose, 13-14 for maintenance and 15-16 for weight gain. All of these are useful to consider, and all of them are wrong. Ultimately, you'll need to figure out how much you're eating, modify it so that you're eating something good, and then modify quantities until you're losing about 1lb/wk (making 210lb a 12 month goal, maybe longer if we're going to be honest and take into account stalled progress, which happens). In theory, this works out to a calorie deficit of 500kcal/day (so, if you need to be consuming 3,200kcal/day for maintenance, you'd be consuming 2,700kcal/day to lose weight), but again the calculators are generally inaccurate, so that makes it a lot harder to figure out your baseline...that is, unless you do something completely crazy like figure out how much you're currently eating and how that's affecting your weight, and then go from there.
To do that, start tracking your food intake: track everything that enters your mouth, and how much of it you eat. Do this for 7 days, and then figure out the average daily calorie consumption across the week (one day might be 2,000, one day might be 4,000, so add up all the numbers and then divide by the number of days to figure out the average). Weigh yourself at the start of the 7 day period and again at the end of the 7 day period, in the same conditions. I recommend getting up in the morning, peeing and pooing, then standing on the scales naked without having had anything to eat or drink. It's not fool-proof, but that's pretty much the most reliable means of measuring body weight. Assess the change (if any) in your weight over the period of the week, and adjust calorie consumption accordingly.
There are even simpler methods of figuring out your diet, but this method is good at getting specific in the context of your own body which, in theory at least, makes results a little more reliable.
