Have you looked into HIPEC? As far as aggressive treatment of peri mets, HIPEC is probably at the top of the list. I have no personal experience with MDA, but from what I understand, they have very limited circumstances in which they recommend HIPEC. It sounds like your husband has extensive disease, so he is probably outside their parameters. Again, I have no personal experience with MDA, but that is what I have heard.
I have had peri mets. I have had HIPEC. I did not have extensive disease, but I have also had liver mets. Perhaps an outside opinion wouldn't be out of line. You never know, with an aggressive surgeon...
As for the reliability of PET... I have had negative PETs, right before surgery, and there were indeed tumors inside me. If cancer is currently beaten down by chemo, there can be little to no uptake in the images. Take away the chemo, and a few weeks later will probably be a different story.
CEA is a good marker for some, not for others. So, how important it is, is kind of dictated by the individual. For me, if my cancer is growing, my CEA skyrockets. It will drop into the normal range if my cancer is either surgically removed, or beaten down by chemo.
Best wishes, any questions, please feel free to ask!
stg IV 4/2013 @34 - liver, ovary/peritoneum
Lots of chemo, surgery and good luck - still doing well 03/2016...