I'm in the same boat as you. I have a similar post with the title "Are these ready to be taken off? PICS" So you can have a look at my pics too if you want
Aesthetically, I think your teeth look stunning, they look amazing. I am jealous to say the least. But I do agree with you that your midline is off. I can't really tell there is a gap between your lower middle teeth, but I'm sure you're not making it up. If it bothers you then it's not right is it?
Is there any reason why your ortho thinks you're ready for them to be taken off? I'm going overseas in 5 weeks for a period of 5 months, so I have a feeling my ortho wants to take them off before I go away. But I couldn't care less if I am still braced while I'm away. Certainly they can keep them on for that long.
About you saying when you lick the back of your teeth and they don't feel straight, I can share this feeling with you. Although I think this may not be a matter of straightness, I think it's just a matter of my teeth being different shapes and sizes, so rather them being flush at the back, they make them flush at the front, therefore making them look straight.
Good luck. Perhaps just voice to your ortho that you do not feel comfortable having them removed, and politely requesting that he give it a few more weeks to see if he can try to straighten your midline a little bit.
Good luck and let me know how you go.