Test the fabric before you do anything. Some cleaning products are great for one type of fiber and ruinous to another. Because you have the garments, you will be best equipped to determine fiber! Here is our guide -
https://vintagefashionguild.org/resources/fabric/determining-fiber/
The style of the blouse/jacket top looks 30s, but the cover/dress/robe looks far more 40s.
The painting looks hand done, and likely not by the manufacturer. It would be very hard to say without feeling the garment and the texture of the flowers, if it would be possible to soak. Sequins can be tested - clip one or a part of one off and leave in a dish with water. Some older sequins are gelatin and will melt. Others are not gelatin but will bleed out their colors. Better to test independent of the garment so that you don't risk damaging everything at once! If they cannot be wet or cleaned, best to remove entirely, if you are going to clean the garments.
As for the potential blood or rust, this will be difficult, but depending on the fiber - it might be possible? Many nightie/combo/robes were made from Acetate and just don't hold up great to many stronger cleaning products. Acetate can dry out easily and then shred. Silk may also shred if dried out and then wetted. Best to see what you are up against and how much of a commitment you want to put in. I think this is a lovely set, and if you were planning to sell it anyway, you would likely have a buyer willing to take on the massive cleaning challenge. If you are keeping for yourself, just go slowly, one piece at a time, and figure out by testing the fiber and then testing any cleaning ideas in the most inconspicuous spot on any of the pieces.
I use Whink for rust - but it is quite harsh and I would not start anywhere near the Whink bottle on these! I think the most gentle product, Castillian soap flakes, would be a starting point.
