What are my chances at MiT, CalTech, Harvard,...

A 2270 is “ok” (and just “ok”) for MIT.
I’m going to be frank… if you need to “study” to raise your math SAT above a 670, then a top-tier STEM program is likely going to be too much to handle.

If you did get into MIT, you would find that most of your classmates got an 800 walking in cold.