Hi,
i am no expert but looking at your drawing common sense tells me that your Z is definitely weak, the bed also.

Interesting that last night i was contemplating the way i could do something similar.


IMHO:

-Forget about that fancy ribs on the Z. Use Triple profile welded together and reinforce it with say 60x10mm or even better 100x10mm ribs without undercutting them for "looking good" purposes . Or make it all from 100x10mm plate welded together, with ribs and so,, or why not even 20mm thick where needed.

-fill the bed with profile, don't leave empty spaces there. Only empty space should be for the ball screw to pass. Fill the empty spaces with short profiles perpendicular to the other.