You poor thing, OP. I do wonder if something else was going on though because unless there's something not covered in my (extensive) lactation library I can't find anything that explains your cardiac symptoms and the extreme nature of how ill you got. Maybe another infection going on too and with a stressed immune system you got really, really unlucky. Such a shame :( I'm sorry I can't really offer any help with the bottles, further than has been offered, but you may find this helpful:
www.kellymom.com/bf/pumping/bottle-feeding.html
And if you've not used powdered formula before:
www.food.gov.uk/multimedia/pdfs/formulaguidance.pdf
Hope this is of some help. On another note, do you know how to gently reduce your supply to avoid another bout of mastitis as you wean off the breast? Bear in mind that taking your time over it is most important, and just gently reducing your supply over time. At the first sign of either blocked ducts or mastitis keep up the expressing and see it through before trying again.
One other thing is perhaps to check on the safety of the meds with the Breastfeeding Network as Truthsweet suggested, and maybe switching to safer ones if necessary, for the duration of weaning, so that the expressed milk can be used to give to your baby (every drop counts). I think a lot of mums feel better about weaning if they're a bit sad about it when they can at least not be expressing and throwing it away.
Best of luck :)
badger - no, I know, I've been so exhausted with the bub2b and my other boys, trying to get as much through my training as poss (just posted Mod2), and trying to set up a Breastfeeding Welcome scheme in my area as well as other BFing projects that I've got on the go. Plus I'm really busy with UKAMB stuff right now. I really miss MN :(