Sedentary or lightly active?

Quick question: I'm a college prof and I spend a good portion of my days either standing in front of a class or behind my laptop. For that reason, I would say that I'm "sedentary." My question is, does this go up to "lightly active" if I lift heavy for around an hour 3 times a week? (3 1-hour workouts)

I'm just trying to figure out how much I should be eating. I'm on "sedentary" and losing weight right now, but 1500 calories/day has left me a bit rough around the edges. I've started noticing a slight decrease in strength that even translates to my lifting, which honestly worries me a little. My BMR is apparently around 2400-2600 calories, but I'm not sure if I believe that - I was eating around 2000 calories a day while keeping the same workout routine and didn't notice much change (muscle became more prominent, but weight did not really change). If I go up to "lightly active," then the app gives me another 300 calories to use - I just don't know whether it would be wise to factor in a larger activity level if I'm where I need to be right now.

Oh, and here are my stats, in case you need them:

Male
26
230lbs
5' 8"
Body fat %: 28%

Any advice that people can offer would be much appreciated - thanks for your help!