Hi insearchofsweetdreams,
I don’t know how firm this mattress would feel for you or how well it would match your specific needs and preferences in terms of PPP (Posture and alignment, Pressure relief, or Personal preferences), especially without a reference point of a similar mattress you have tried that I could use as a reference point, because firmness is relative to each person and their body type, sleeping positions, and preferences and sensitivities and there are too many unknowns and variables involved to use specs (either yours or a mattress) or “theory at a distance” for anyone to predict how soft or firm a mattress will “feel” for someone else (see mattress firmness/comfort levels in post #2 here). If you have a more extended phone conversation with the retailer or manufacturer then they “should” be much more familiar with how the mattress is likely to feel for different body types and sleeping positions based on “averages” than anyone else.
The specs you listed are “close to the edge” but are still inside the guidelines here which means that there are no low quality materials and I wouldn’t consider it to have any obvious weak links in the design for most people that aren’t in higher weight ranges.
Phoenix