Hi,
Let's meet on Friday, at 7.30, in front of the John H. statue.
1) Do I need a comma between "Friday" and "7.30"?
You can use two commas like the example, or just one after '7.30', or even none. As a general comment, my opinion is that modern English tends to be 'simpler' in terms of punctuation, so that fewer commas are used in situations like this than were used in the past.
2) Are you available ;-) Yes, but how will I recognize you? Can you carry a grammar book in one hand and a dictionary in the other, please?
Best wishes, Clive