Pumping mummy's

Do it now. You can pump to freeze it so you can start making a stash so others can take over feedings. And while he was on bottle while he was newborn (he didn't latch right so I pumped all the way up till 6 months and formula fed the rest of the way to a year old), I just fed him every 2-3 hours and when he gave hunger cues. As for introducing a bottle see if he takes to a pacifier. It may make the transition easy. 🙂

Would not recommend the pacifier mentioned above, if you're not using one already. They're normally for badly behaved children, and yours isn't from this description. Once you start on that stuff, you'll have to wean them off it in 6 months. They're a nightmare all round. Don't do it.
There are probably averages online of what you should be giving (or on formula bottles for reference). However, as you don't know what your baby drinks, you could add a bit more in the first few times, to see how much they want. Mine used to go above average when having a growth spurt for example. I never liked her drinking a bottle to air (empty).