Sia 's estranged husband Daniel Bernard is seeking a TON of spousal support ... asking a judge for $250,856 per month, TMZ has learned. And that's not all ... he's also asking for Sia to contribute at least $300,000 toward his attorney's fees, and an additional $200,000 for forensic accounting fees and costs ... according to court documents obtained by TMZ. The "Unstoppable" singer filed for divorce from Daniel in March, citing "irreconcilable differences," and he claims they spared no expense