Regarding appliances, you have tax amortization schedule. But, you need account average for an year.
If vacancy reduces income, naturally you need to account vacancy, but fairly accurate vacancy.
There are two ways to calculate Cap rate. 1) With assumption 2) with actual values (tax filed). The second one is more reliable than assumption one as many assumptions are balpark values.
For example, you said "allow 1 month vacancy for each year". Never faced vacancies, more than 5 to 7 days, for the last 10 years except first month after purchasing a home. This is mainly to make it as move in condition gap.
Cap Rate is an indication to see whether you are getting right cash flow return on your investment. You need to have fairly accurate value to get cap rate. Otherwise, you may see low cap rate and will miss buying a real estate !
In cap rate, all income and expenses are actually calculated except mortgage interest.