I think you should let the medical professional take care of your 46 old brother's situation first;let them to see what kind of medications he should take to increase the "blood count" before using injections to help boost the counts.
First, there are different injections for different conditions. I am not a doctor,but I know about injections in the pharmacy. You did not mention which one(ie; WBC,RBC Platelets,Hb etc.)that had low blood count in any of the messages you wrote on this board. You only mentioned about folic acid and vitamin B12 prescribed by the doctor and most likely were for anemia .
"fluid in the belly" as you put it ,in general,will not affect that much in the decision making process for the oncologist. Up to 21 liters can be safely removed from the patients in the hospital setting without complications. However most of the amount that removed are much lower than that.
Intrahepatic bile duct cancer(the cancer started in the bile ducts in side the liver) is what your brother has; it is different from the liver cancer(ie: in cytology and histology when under the microscope.)
Missing one or two treatments may not make much of the difference in the plans of oncology treatment. It may help your brothers "blood count" back to normal and can receive the chemotherapy.
Nobody can recommend oral chemotherapy to you except your oncologist; Oral chemotherapy agents and especially the targeted therapy agents taken by mouth are potent medications( ie; both in effectiveness and side effects) and should not taken them lightly or think of them of less potent than the IV formulation.
I hope my specific answers to your questions will help both of you and your brother to develop a more positive attitude toward the treatments and outcome of this diseases.
Finally,I can only speak for myself, positive attitude helps me a lot in dealing with this cancer for the past 44 months; it change my outlook toward my disease and helps me to start a new journey for the rest of my life. It is no fun,but take the best that you can have and prepare for the worse that you cannot control through communication with others and learn about the disease. You will never know what will lies ahead of you,but if you try, I am sure your effort in prolonging your brother's life will not be in vain.
Please know that my personal opinion is not intended nor implied to be a substitute for professional medical advice. If provided, information are for educational purposes.Consult doctor is a MUST for changing of treatment plans.