Good to hear your supply is ok. I think he is wanting to feed more regularly, but not necessarily for longer. If he bites you, take him off and put him in a different position. If he asks you for more feed, offer it - but only once if he bites again. Then offer a toy that can stand biting
He still has a couple of growth spurts to do before you get him established on solids. Usually they are at about 3mos and then four weeks later. I find my babies have growth spurted every 2 weeks until 10 weeks and then at 3 1/2 and 4 1/2 mos. So you might have two or three spurts between now and 5mos. Totally go through with demand feeding at his age.
I disagree with your mother on the crying rule of thumb. I won't leave any baby to cry for more than 10 minutes. At 11 weeks I'd be more inclined to settle for 5 minutes. It's enough time to tell whether he is overtired (crying settles down) or he needs something (food, change, not tired) (crying gets more frantic).
I have found Plunket centres really good for this stage when you need another adult to ask questions. You can go down to your local office and just live there for a day and ask them for advice when you are stuck. It's a nice change of scenery too