With 1500 transctions / 10minutes, we are only getting 2.5 tps.
Correct. The reasonable expectation of tps for 1 MB blocks is somewhere between 2 and 4 tps.
I thought in theory we should be able to go to as high as 7 tps??
Correct. That's the
theoretical maximum. That assumes that everyone is using compressed key addresses, and that
every transaction is minimal size (1 input and 1 to 2 outputs).
Realistically,
average transactions are quite a bit larger than that.