7.5 months is really very young. Some of what you are saying is still pretty typical for an infant this age, or at least you haven't missed the milestone by that much, I believe. Is this your first child?
Here's my advice...bring your concerns up to your pediatrician and keep watching. Not like a hawk, and not with anxiety or tension. Just watch. Babies develop differently and sometimes even early delays are overcome (my daughter did not speak at all until about 2 and did not join any words together until around three; she is now above her peers in verbal skills at the age of 9, and has been probably since she was around 5 or 6).
That being said, I knew both of my kids were "different" from earlier than 7.5 months. However, I have had other friends who had "different" babies who went on to have no notable differences from their peers.
At any rate, I, personally, do not view autism to be anything to be dreaded or feared. So while my best advice would be not to worry until you have a concrete reason to worry (my daughter had many of the same symptoms you are sharing when she was approaching 2 years old...poor response to name, no words, didn't seem to understand what she was being told, no interactive play, no imitation, etc), you needn't "worry" anyway. Autism is not the end of the world. It is a different way of being.
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Mom to 2 exceptional atypical kids
Long BAP lineage