Congrats on your weight loss!After you lose a bot, there is always that urge to keep losing- yopu have to fight that! You are in a completely healthy weight for your height, and even if it isnt all muscle, as you say, you are at a thin weight! Try not to lose much more, or better yet no more!
Since you excersise much more compared to me (same height as you), you should prolly eat a lil more than me, but you'll have to try for yourself. I eat around 2300 Calories a day, with 3 meals (600 Cals) and 2 snacks (one 300, one 250). When you increase your intake though, dont just jump to 2300ish. Go up over a short period of time, in intervals (ie/ add 500 Cals every 2-3 days). Hope this helps!