This sounds so similar to me--but I'm an 84 year old woman, but like you, very healthy--no medications except for glaucoma. I was sick as a dog with the chemo--never have recovered my weight (almost 2 years--120 pounds to 95). It was the chemo with the FlorETC--I'm not as good with the medical terms as some, but the pump at home 2 nights; had to quit after 2 sessions and went for the Whipple. Like you, my antigen was 153.
THIS IS AN OPTIMISTIC NOTE TO YOU. I never went back to chemo, though strongly encouraged to. One year after surgery I had radiation for a mesenteric mass--now it has decreased as the radiologist said it would. I have been feeling great for over a year and have decided to only do radiation, which had minimal side effects if any. I have read several other positive results from radiation--PLEASE LOOK INTO RADIATION, the new type that targets. I only knew about it as my 85 year old husband had it for prostate cancer, sailed through it for one month driving himself 50 miles for treatment. I was impressed--no return of his cancer, but ongoing tests of course. I kept asking my oncologist about it, but on my own saw the radiologist who did not promise anything--did not want to compete was my impression. But I have read in this group that others have had good results with minimal life style impact.
I like what "marky..." has written you. I say the Whipple first; you will have new information then about lymph nodes, etc. so you can make a better decision about chemo. And look into radiation; not always recommended by oncologists (mine didn't) as they legitimately want to cure and wipe out every bit of cancer EVER. My radiologist did not promise that, but frankly I'm reading many who have recurring cancers after chemo too.
It has been 2 years since my diagnosis and I am having a normal life, feeling good, impressing my friends who thought I would be a goner. But 2 years as an 84 year old with no small children is way different from you--I'm thrilled for these years. I understand you have a life ahead of you--just look into radiation and immunology too. I think they are the future of cancer treatments. Best wishes...you have a good attitude and are facing the problem. You will make it and be there for your family.