How do I negotiate this offer?

So I recently was made an offer, but I have several concerns:

1. I applied as a Packaging Engineer, but the title they are offering me is Packaging Specialist. (Can they do that?)
2. They made an offer of $50,000 which is much less than I was expecting. Would I be out of my mind to ask for $75,000 when the average salary for a Packaging Specialist is $69,000 in my area?
3. Should I continue this conversation through email or phone?

Thanks in advance for any advice

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