Congratulations on your new baby. I don't suppose this will really be helpful but I'll try. This is a counsel of perfection - most people won't have the opportunity - but I'm putting it forward anyway.
To boost your milk supply quickly, I suggest three days in bed with the baby. Do you have someone who can look after your older children? You need to do nothing in the way of housework or childcare, just focus on milk production.
Baby constantly at the breast, no need to time each side, just switch when you feel.
For you, enough to eat and drink but not too much. I used to take a flask, bottle of water, sandwiches. People always recommend nuts - you could if you like but urgh, I hate the things.
When the baby is asleep, express - relax and don't worry about how much you get. Just do it for fun. It will really build up your confidence in your milk production capacities. You're an experienced mum so I won't go through the very basic 'how to' but pm me for that if you think it would help.
Don't worry about topping up with formula. Its ok. Babies have had formula and then gone on to be exclusively breastfed and have fed for years. I know two such babies, very well.
Stop worrying about being engorged or not. I know its an amazing feeling, if I could go through it again tomorrow I would, but for some people it doesn't happen, particularly if they have breastfed before. Your body is used to breastfeeding, that's all.
This isn't a test, you can't 'fail'. Its ok.