Terrence Howard -- I'm Too Broke To Pay My Ex ... I Live On $6K A Month

Terrence Howard's ex-wife threatened to blackmail him to get a RIDICULOUS amount of spousal support -- or so he claims -- leaving him with a scant $6K a month ... and now he's gunning to undo the injustice.

Terrence filed new court docs ... asking a judge to throw out his divorce settlement with Michelle Howard. He says they were only married a year and he was extorted and blackmailed into signing the settlement.

Michelle's not backing down, claiming he owes her $325K in spousal support.

Terrence claims he could never pay her that money ... because he only takes home $5,878 a month.

Howard claims the balance of his earnings are earmarked for another ex-wife, Lori McMasters, to pay spousal and child support.

Howard says he's actually an employee on Lori's payroll -- his Hollywood movie money goes directly to her ... and she cuts him his monthly check.