I can only speak to the radiation issue. They typically give a person their "lifetime maximum radiation exposure" in the area being treated. Even the skin is in greater risk of skin cancer as a result (after receiving radiation therapy one must avoid sun exposure and use sun block for the rest of their life).

They can re-treat certain areas under 2 conditions:
1. That the person hasn't received the full dose (some persons receive 50 cGy - if they received the full amount then they received the "boost" as well bringing the radiation to a total expeosure of 72 cGy). In other words, if you haven't received the full amount, they can come back later and give you the "boost". If they were treating a stage III of IV they likely gave the lifetime dose already;
2. In some cases they can re-treat if IMRT was used initially, but not in exactly the same spot.

IMPT is SO accurate that they give IMRT with it to have safe margins. Certainly worth investigating. I am not surprised the doctors didn't mention IMPT, although it has been in use for 10 years, only 2 facilities in the US have it. MD Anderson is spending 125 million to install one there. Whereas a LINAC is under a million.

There are many reasons why radiation has limitations. Among them is that it cause cancer and irreparable damage to the healthy tissues. When they determine the fractions (daily dose), consideration is taken to how much radiation the healthy tissues can absorb and their ability to heal between sessions. It's all about risk/benefit. When they exceed the maximum dose rate the risk exceeds the benefit.

And it's ok to be mad at God. If anything can cause a "crisis of belief", cancer has got to be at the top of the list. I am sure that God is ok with that too...