What? My advice was the best! Escape to North Korea... or you can escape to Cuba, whichever suits you the best.

try some bjj (brazilian jiu jitsu) and put him in a chokehold

bjj is the best method of fighting someone twice your size, that's how royce gracie used to beat everyone back in the day

Hit him in the neck. Fast and hard! That's the best weak spot.

So this a matter of "honour". I am curious. What happened, exactly? Most people who use that reason merely have their own pride at stake.

just try to wear him out, and aim for his head and legs. hes going to rush you so try to dodge at first and catch him off guard.

also since he is sensitive about his weight, call him fat and mock him, make him angry so he does something stupid, but make sure you are ready to dodge his rage charge.

Ive done MMA for a number of years and my quick advice for a street fight with a fatty is; 1) Learn to punch if you dont know how to. If you know how to throw a punch it will end the ordeal as quick as possible cause you will maximise your power. 2) Keep your hands up in a guarding position unless you are punching. Keep your fists to your face if not punching. If you are punching with your right make sure your left hand is glued to your face and vice versa. 3) Be aware of your balance/wrestling. Last thing you want is a fatty bull rushing you and you not having your base and you get forced on your back(if you dont know how to fight off your back like most, you will be fucked). I would look up a video of ''sprawling" if you do not already know how to. A good sprawl will turn that bull rush into top control on the ground or in the very least allow you to stand up. This is all assuming his friends dont get involved. Good luck.

edit: Also show no fear, no matter how much is in you. The mental aspect of fighting can be a huge area of leverage if used correctly

It sounds like you have very little if any experience fighting.

Do not watch any particular style of martial arts, the technical aspects are too complicated to pick up in a few days. What you want to watch is MMA, specifically old pride matches. Pride did not have weight divisions so you could get tiny guys fighting massive ones. You want to go on youtube and find those fights to see how the smaller guy approached the bigger ones.

Do not try to learn any complicated moves, just stick with the basics. He has such a size advantage of you that if he gets a hold of you and brings you down the fight is over so remember that.

Give me a better idea of your sizes. How tall is he and how tall are you? I know you said hes like 240-250 but how much do you weigh? Also where do you live?

Just use an outboxing style to move around while using a few quick jabs to keep him at bay if he charges and use your speed to get a few counters on him when he starts to run out of energy with his swings becoming wide.