I'm a little concerned for you that if you meet him face to face you'll end up giving in (people pleaser) and just carry on doing what you're doing.
Yes, it's the professional thing to do and yes, if you can be strong enough to stand your ground it's the right thing to do - but is it the right thing to do for you? I'm not so sure.
Family and friends can be right arseholes when it comes to business and they DO play on your emotions because they know they can. You have to toughen up - this can be your test case of saying "No".
I went on an assertiveness course once through work - it was fascinating watching how some people would figuratively let people walk all over them.
First exercise was in pairs - one had to say to the other "I really need £5, can you give me £5 please?" and the other had to say No. Some people literally could NOT do it. Couldn't bring the word out. It was shocking! 
I honestly would cost out how much money's worth of work you have already given him, so that a) YOU know, and b) if he continues to browbeat you, you can tell HIM. SOmetimes the numbers can be very shocking, so it might stop him trying to leech off you more (and it might make YOU realise how much he's already had off you and what you could have spent that money on if he'd been a paying client!)
Have your T&Cs worked out on paper before you meet with him. Hand them over to him and say "this is my rate, these are how many hours I have available for you routinely and here is the contract for those hours. Extra hours are at this rate (1.5x original) and calls out of business hours are charged at this rate too."
Takes control of the discussion - he can negotiate the hours but not the rate - and shows you mean Business.