“Myself and spouse are separated but still living in the same apartment.”-I am not quite sure about your situation; spouses can make a contract with each other about how they will behave while they are waiting to get divorced a separation agreement, but the one-year clock does not begin to run until the spouses are living apart. For example, in NC the only grounds for divorce is when the husband and wife have lived separate and apart for one year.
“1. Do I have to report the entire rental income & expenses or only 50%. “---->I assume that you file your return as MFS; then it depends; you cannot deduct any property taxes or mortgage interest unless YOU paid it. If a co-owner or cosigner (or even a complete stranger) paid the taxes or interest you cannot deduct them even though you might be an owner of the house. So, to deduct your rental expenses ,i.e., real estate taxes, interest expenses or etc, the taxes must be imposed onyou taking the deduction. In particular real estate taxes would be imposed on the owner of the property. The Tax Court has allowed beneficial owners to also claim the deduction. Since the 1098 for the mortgage interest is sent using just one SSN,I mean the PAYER’s SSNon the Form, the general rule is that the person whose SSN is on the form is the one claiming it. If both of you are contributing towards the mortgage payment, then you can split the mortgage interest (how you split it is up to you) and you would need to attach a statement to both returns showing the split.
“2 I am aware that since we did not live apart, I will not able to deduct any rental loss.”--> I am not sure. Is this right??
“ Is it possible to use most the entire mortgage interest and property tax amounts on schedule A?”---->As said above; it depends on the situation.