Personally, I find the estimated calorie burn from my Fitbit pretty accurate. If I eat to what it tells me, I lost weight. I mean, it isn't going to be perfect to the last calorie, so I'm not slavish about it, but it is a decent enough guide.
How tall are you, Kiko? Because that's roughly what my calorie burn is according Fitbit for this steps. I'm 5"9 and currently 12st 11lb.
Not, honestly, that could have been written about me, 13st and burying out of my 14s. I got to, and maintained at 11st for my wedding, and it only went to pot when I got pregnant. I've never got anywhere near since, largely because of lack of motivation. I'm very much in the zone now, with a better understanding of my triggers for over eating (largely stress and boring food!). I think breaking your goals down into smaller chunks is a great idea. That's why I'm aiming for just under 12st to start with, then I'll push on to just under 11st - which is a good weight for me. When I get there, I'll be interested to see which of my 'thin' clothes fit - I bet I'm a very different shape now!
Last - woo hoo! Awesome job! Have a virtual high five!