Tell your daymom that she is an idiot and that you trust your paed and midwife more.
Studies have shown that unlike formula fed babies the volume of milk a breastfed infant eats does not change much after 6 weeks (it will increase slightly during growth spurts but will settle back after a few days) this volume is 750-800mls milk per day in an average baby (whether 6 weeks or 6 months).
Often though when babies are bottle fed, milk comes out too rapidly and "full" cues are often missed. It doesnt help that we have a culture of finishing up.. This is also why often babies who are fed regularly from bottles are heavier than those fed at the breast - whether the bottles contain breastmilk or formula.
200mls is a huge amount per bottle. James has never had more than 120mls at a time (but then hes only had about 10 bottles his entire life)
Your daymom might be missing cues. Why dont you ask her to offer smaller amounts per feed over smaller gaps - maybe freeze 100ml increments and ask her to feed on demand. (sucking on hand, trying to root etc) She might be feeding to pacify when he is agitated.. Another thing to try is to stay with newborn teats which are hardet to suck though and slower flow.
At 5 months he is still quite young, and I have no idea where he is developmentally, but milk is more nutrient dense than a teaspoon of yoghurt or a bit of fruit. By increasing solids too quickly you may displace some of his milk requirements, which can result in dificiencies. Also by using food to displace milk you might cause premature weaning (ie before 1)
It sounds like your daymom has never looked after an ebf baby before though and she may not understand that breastmilk is digested far quicker than formula and that breastfed babes do routinely feed more often than formula fed ones. If she continues to give you grief, maybe point out to her that babies managed just fine before nestle produced formula, Maybe give her this page:
milkmatters.org.uk/over-101-reasons-to-breastfeed/