Are my calories too low?

Hi everyone! I’m actually looking for some advice here. I’m a 22 female trying to loose weight. I started at 240 and I’m currently around 180. I was at 175 but the holidays made me gain a few pounds hehe. I’m 5’4 and my job is really sedentary so I don’t move a lot if at all. My TDEE is pulling up around 1850. And a 500 deficit would cause me to eat at 1350. Is that too low? And what happens as my weight shrinks. Won’t my TDEE go down which will actually shrink my deficit and then I won’t be losing 1 pound per week? I’m trying to get to my goal weight of between 140 to 145 in 6 to 7 months. I like the way that I look right now, but the scale says that I have around 110 pounds of lean body mass so that I’m basically 40% fat, which is discouraging. Anyone have any advice on how to stick to my timeline without starving myself because I don’t want my body to basically crash its own metabolism.