If I'm traveling with someone, should the amount of accommodation in the visa application be my half or the full cost? For example, I'm traveling with my dad and he's funding the entire trip; should I put half the cost of the accommodation, as we will stay in the same room?
Applications that are part of a family group only require that the primary submit evidence. Other family members should put the primary's GWF number in their individual remarks section.
As long as you have recorded your father's GWF number you can put 0 or half, it doesn't matter. They are smart enough to understand how families travel together and nobody gets refused for putting an artificial number on accommodation when they are travelling with a primary.
You can still be refused on other grounds, but those grounds will not have to do with something so mechanical as what you put down for accommodation expenses.
There is also the situation where the primary is refused and you are issued the visa. If that happens you will have to ask a new question.