Hope you'll find something that works, even if only augmenting your current treatment
On the other hand those are all feelings and I’m not trained in medicine.
That's a gross mis-characterization of keto diets, at least when done properly[1].
Up to 20g of net-carbs (ie: non-fiber) per day. The intention is to moderate your insulin response, which impacts other hormones and, for weight loss, switches your fat cells to be able to release fat for energy instead of storing fat. That level of carbs are more than adequate to maintain necessary blood sugar levels for your body's needs.
There's no "weird starvation mode". Lowering your carb intake and moderating your insulin response causes your body to stop the "easy" burning of carbs for energy, and to switch to burning fat (from your food first, fat cells second) for energy. A big misconception about keto is that you have to eat a lot of fat; if you're trying to lose weight that's not true. You need to consume enough fat to keep your calorie intake from being too low (otherwise you do get into a starvation mode which lowers your metabolism), but low enough so that your body needs to get fat from your fat cells to make up its energy needs.
All that said, I have no idea if keto helps with cancer at all. It almost certainly has no direct affect. If there's any benefit, I would guess that it's related to the hormonal and metabolic impacts of fat-burning rather than carb-burning, or the reduction of systemic inflammation that most people on extended keto diets experience.
The rationale to put it shortly is that cancer (amongst other modern disease epidemics) is a mitochondrial disease, that most cancers have damaged mitochondria and can't process ketone bodies. Ketogenic metabolism is perfectly healthy and most probably the default state for human biology. I won't go into details in this reply, but my personal experience and that of thousands of others attests to this.
The rationale for an animal (and animal fat) based diet is more complex, but it revolves around the fact that all plants contain compounds that damage the intestinal lining to varying degrees. This leads to a cascade of events in which the immune system devolves into a diseased state that leads to the wide array of chronic illnesses that we see today. Chronic inflammation disturbs the whole system, often includes neuroinflammation, which itself causes depression and exacerbates stress, worsening the condition further.
As for keto diets and cancer, there's been a lot of studies claiming all kinds of things. I have trouble trusting diet related studies, as they constantly contradict each other and probably have far too few subjects versus the number of variables, which they often can't control. But as for the theory, I think at least for particular cancers it is believed they need sugar to grow, so can be starved by a keto diet.
Cancer cells rely much more on glycolysis than oxidative phosphorylation (respiration, basically breaking down sugar with oxygen). You get a net of two molecules of ATP from glycolysis compared to 30 or so from respiration, so you can expect that cancer cells need much more sugar than normal cells just to survive. https://en.m.wikipedia.org/wiki/Cellular_respiration
Second, glucose competes with dehydroascorbate (DHA, oxidized vitamin c) for glut1/3 transporters. DHA gets transported into cells (in particular RBC's) to be reduced back to the anti-oxidant form by glutathione: ascorbate. Then that ascorbate molecule can remain in the cell acting as an antioxidant or be pumped back out of the cell to the blood, etc.
If DHA doesn't make it into a cell quickly it gets hydrolyzed and excreted and you lose that molecule of vitamin c. So chronically lower blood sugar is expected to conserve your vitamin c and allow higher ascorbate levels, especially within your cells.
This can have all sorts of beneficial effects. Strengthened collagen makes it easier for a tissue to heal/encapsulate the cancer and harder for it to metastasize, quenching free radicals can prevent damage to surrounding tissue, etc.
But also, cancer cells accumulate more iron than normal cells: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5983609/
Ascorbate can also reduce Fe3+ iron to the Fe2+ form. That Fe2+ iron can then undergo the fenton reaction to form free radicals: https://link.springer.com/article/10.1007%2FBF03033342
Those free radicals can go onto to kill the (high iron) cancer cells. For this reason vitamin C kills almost all cancer cell lines in vitro at doses that do not harm normal cells: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2516281/