Mattress Recommendation w/ Greater Flame Retardant?

Good Day! I am seeking a mattress with high flame retardant functionality. I understand that many currently recommended mattresses offer flame retardation solely via a fire resistant cover, such as wool. However, I am concerned about the flammability & high burning temperatures of untreated memory foam or latex in the event that a fire were to penetrate that barrier. I’ve been reading these forums (thank you Phoenix for your posts) to learn about mattresses & safety, but also have been reading some studies on mattress burn temperatures and incidents. Perhaps I am being anxious & overly cautious - but I would rest easier feeling more safe on my mattress.

I currently use a local store-brand Innerspring Hybrid Mattress (the Mancini’s Tahoe Plush) which I am happy with but has since been discontinued. I would describe it as a medium firmness mattress. However, I am looking to move to a queen mattress at this time. I am a mid-sized back sleeper and my partner is a smaller side-sleeper.

We’ve looked at some chain stores in our area, and so far innerspring hybrid mattresses have appealed to us. However, we are mostly seeing Kingsdown in stores which I understand is not typically a recommended brand. I would also be interested in a pure latex, such as SleepOnLatex, if not for the above anxieties. I think a good solution would be a reputable mattress that is innerspring/cotton, or a chemically treated hybrid or pure latex with CertiPur certification. I would really appreciate any recommendations in this area, I have been researching but everything reputable I have found appears to be untreated on the inside. Our budget for a mattress is $1.5K.

Thank you very much for your time!
-JM

Mancini Tahoe Plush Features (Current Mattress)
• 4 way Stretch Knit Fabric
• High loft Fire Barrier
• 1/2 inch Quilted Visco Gel Foam
• 1 3/8 inch Convoluted Foam
• 1/2 inch plush poly foam
• 1/2 Talalay Latex BB
• 800 series Foam Encased 8 inch 3-zoned pocket coil
• 3/4 inch lift pad