If its a 2013 then do you have a bolt at end of each footwell and a bolt/screw to the side of the knee?

Later cars had additional fasteners.

FYI - There is also a bolt that is directly below the boot lid Dzus fastener - this is on the underside of the body going thru a chassis tab then thru the wooden body frame to clamp the body to chassis. (always interesting to find no chassis tab - especially on m3w's that have had a chassis change due to nothing fitting quite right)

The knee 'fasteners' can either be the a course threaded stud to screw into the body with a threaded section to accept the double nut (?) to clamp the body to the scuttle chassis tab or much more common is a countersunk wood screw (various sizes) with a washer.....If its spinning then basically the wood frame has 'stripped'.

The torque setting....tight is it.

And your correct they won't always tighten after 13 years...hence the wood screw (s).

For Rattles I would check:
The fuse box cover - put a rubber strip/foam pad under the returned edge on bottom and sides.

Bonnet front corner both sides (the front cowl part) - put a self adhesive pad on the body where the rubber plug is (if fitted/still there).

And don't forget to check the chassis for cracks as this will also create rattles and creaks.