With multiple states is federal income deductions split based on where you work or you live?

Both.

This is the general rule: The income is work state (WS) source income since it was earned there. Resident States (RS) tax all their resident's income, regardless of where earned. You will file a non-resident tax return for the WS and report the WS income. You will file a full year resident return for the RS, reporting all your income. The RS will give you a credit, or partial credit for any tax paid to the WS.

If you have a reciprocal state situation, the answer is different. See https://ttlc.intuit.com/questions/2895760-which-states-have-reciprocal-agreements

For more specific advice, please identify the states. The rules vary. For example, ther are a handful of "contrary states", where the WS gives you a credit, instead of the RS.

Thanks very helpful! Are Indiana, Illinois, Michigan work states,  or resident states?

A "work state" is a state you WORKED in.   A "resident state" is a state you LIVED in.  We do not know which is which for you----only you would know where you lived and where you worked.