not sure what state you live in which may matter if you live in a community property state. in that case you may need the help of a lawyer.
then ignore the following
regardless of which of the following returns you file you only report your own income.
if married filing separate to e file you'll need his social security number. without it you'll have to paper file and include a letter explaining why you couldn't get it and his name and address. if you can't find out whether he itemized or not you'll have to guess. the safe method would be the one that produces the lowest deduction. if you guess wrong the iRS will correct your return or ask you to amend
if you pay more than 1/2 of the cost of keeping up a home for yourself and your child who lived with you for more than 1/2 the year you can file as head of household. don't need spouse's info and you can let TT choose the higher of standard or itemized ddeductions. you can also efile