If you HAD to – if the cities around you went kaboom, so you couldn’t easily re-supply, and your husband had no outside work for money – could you make do on the farm? If not, what would you need to change? (Is that too big of a question?)
Short Answer, just the farm, no, we don’t have enough wood to be able to heat for winter, no, we don’t have enough pasture, hay for everything we have now.
Long Answer, The first thing we would have to do would adjust the levels of the farm critters, we would need to move out the pig, cow and cut down numbers of everything else, I would need the horse, just for hauling wood, and doing more farm work/plowing, it would depend greatly on if we were able to do barter, in which case having the buggy, and the horse could be a great boon.
I would be left with a horse, sheep, rabbits, and chickens, if I was allowed to barter out to the farms around me, then I would be able to trade for the needed wood, at that point, we would be fairly well off in terms of the rest of things.
I honestly wood needed to make the change to more land if I wanted to stay on the level I am at in regards to animals, having said that , we don’t need this many critters to function for us.
Wood for heating is the very clear weak spot for us at this time… Most everything else would work for make do..
Just another Day on the Farm 
We need to get our garden effective, and expand our fruit production. Also, sort out the water issues at our place, and I would love, love a new wood burning cook stove.
Farm girl, you’ve been training your draft cow for two years now, I know you love your Brandy, but why wouldn’t you choose the cow, if you had to? You can still work her a a lighter pace while she is lactating and pregnant, and she will be an easier keeper when she is not growing a baby than the horse. She can do pretty much everything a horse can, just slower. Although, I suppose you already have the sheep and goats for milk, so I can see it would make sense from that angle.
I do not have the ability to keep a bull, so I don’t know how I would freshen her, where I can keep the sheep in milk with the ram, and while I do understand about the cow vs horse, that is the main reason behind that, I would only be able to harvest enough hay for one large critter, and if I have to feed a dry large animal, its alot less required then a large expecting and or producing animal calorie wise..
Would that include water and electricity? What would you do for grains? If you had to rely 100% on your garden, would you make it larger?
Water is good, there would be no power, other then limited solar, very very limited grains, we would need to go straight over to being mainly roots, carrots, turnips, beets and of course, lots and lots and lots of spuds, as well as ideally lots of cabbage. If I had to rely on my garden, there would not be a space spot on my land that was not in some form of production and that would mean that at least another acre would go into production at a min.