What portion of the rental income and expenses do I claim when my husband and I signed a separation agreement September 2017, and we had rental properties together?

It can be whatever split you and your (ex)spouse decide upon. Many couples split things 50/50, but you can choose to divide the income/expenses by a different amount if one person was more/less active in the rental endeavor, or one person contributed more than the other (ex: one person actually owned the property and the other person just help pay for expenses).

The properties were split between my husband and I as per the separation agreement in September.  We each shared 50/50 of all 4 rental properties for the first 9 months of 2017, then each of us took 100% responsibility of 2 properties.  How do I claim my portion of rental income and expenses for 9 months and then 3 months separately?