Thank you for your consult at DoctorSpring.com.
After going through your problems and all detailed reports, my opinion is to go for Surgery and followed by chemotherapy. This is mandatory and is strongly advisable.
Please don't worry about the problems which u faced last time. Those problems appeared to be because of your current problem i.e sigmoid colon cancer.
Your stomach problems and bleeding in stools appear to be from your current problem. Do not delay the surgery and get it as early as possible. This surgery can also be done as laparoscopic surgery. Don't worry please go for surgery.
Hope this helps, If you have queries please feel free to ask as follow-ups.