According to new legal docs, obtained by, TMZ ... the "Selling Sunset" star details what she claims was a marriage in decline for several years-- which reached a boiling point last week when Christine tried to address the family’s financial woes with Christian.

In her TRO filing, Christine claims this set Christian off ... alleging he started throwing a bunch of decorative items at her -- some of which had metal rods in them.

She also claims he pulled his penis out and started urinating right there on the floor ... and even goes on to claim he hurled dog feces at her while he was throwing a fit.

Eventually, Christine says things calmed down -- but the incident convinced her she had to leave him for good ... and so she secretly made plans to do so the next day, wanting to get out of dodge with their young son. Christine says she invited a nanny over the next day to make sure Christian wouldn't lock the property down ... and, presumably, to bear witness.

While Christine was quietly packing her things the following day, March 19, she claims all was calm until Christian suddenly came storming into their room, yelling at her and then throwing a bag full of recyclables at her -- only to miss and strike their 2-year-old son instead. Christine claims there was glass in the bag.

Once the kid started screaming and crying, Christine says she fled the room with the boy and called 911 -- which ultimately led to Christian's arrest for assault with a deadly weapon. Since then, Christine says she's been staying at a hotel ... but still fears for her safety.

There are other allegations she makes against Christian in her docs -- including claims about his mental health, his controlling nature, etc. -- but alleges things got really bad late last year, and ultimately led to this wild alleged incident she's describing.

Remember, Christian himself had filed for a restraining order against Christine -- claiming that the real cause of their blowup fight was her two dogs peeing and pooping all over the house. He denied throwing a bag of glass at her or their kid ... and claims Christine is just trying to manufacture DV claims against him ahead of what he suspects is a coming divorce.

Christine claims that Christian is monitoring her digitally from afar, and in her TRO she's asking the court to force Christian to get his paws off her electronic accounts. She's also requesting protection for their son ... demanding sole physical/legal custody of the boy until their issues can be hashed out in front of a judge, and asking for monitored visitation after that.

FWIW, Christian's TRO request from earlier this week was denied pending a hearing -- and not just that, but the court ordered that he and Christine attempt to work out their issues in mediation. Christine's request for a TRO has yet to be ruled on, however.