The people who made offers and then withdrew are not indecisive. They were looking for something else and your house almost ticked all their boxes. Then they found what they were really looking for.
In order to sell, you have to gauge who might be interested in buying, and then pitch your property to them. You may therefore need to make some changes, because it's easier for your target to imagine themselves in your home if you include elements of what they may already have in theirs. The best changes are superficial ones that won't compromise your lifestyle, won't cost much, and will mute your decor or suggest buyers' existing decor or lifestyle. I agree with people who are saying your potential buyers are elderly downsizers or a young family. So you need to tone down the decor and make the house look less like a place that shouldn't be touched.
Paint the radiator (is that a radiator?) on the living room wall. It should be white to match the walls.
I would not add a bath, not because it is your home and you don't take baths, but because this could be a bargaining point for you - someone likes the house but hesitates because they like a bath, so offer a little discount off the price to make them feel they could afford to put in a bath themselves. Maybe get this job costed by a reputable plumber or contractor so you could persuade them it is affordable.
Add some books. Go to a boot sale and buy some cook books and two bookends for your kitchen counter, and a few hardback books for your bedside tables. Lose the stuffed animals and put out books in the children's rooms. Install large house plants. You could have at least two, no more than three in your living room.
A side table with a lamp that could accommodate some hardback books would be nice too, so the couch doesn't look as if it's there purely for decoration.
If you have an open house, set out a bowl of fruit on your breakfast bar, dramatic plant on your bathroom counter, replace family photos everywhere with books and plants.
(What is the green thing behind the dining table? Apologies if that has been explained before.)