It is an interesting question. But nevertheless, people have been convicted and falsely held in prison for years based on different lines of evidence seemingly leading the same conclusion, which was later discovered to be false. The point is that convergent evidence may nevertheless not be proof, or it may be coincidental, or wrongly interpreted. This will not likely convince you.
I do not believe that C14 is spurious, however. There will be a reason why C14 gives the numbers it does, which will be correlated to varying levels of CO2 in the atmosphere over time, and different rates of formation of C14, which has already been proven by the consideration of the radiation caused by nuclear bomb testing in the past. These things can easily, and have already been shown to vary the ratios of C12/C14 in the known past… but we are guessing about ratios earlier than that (earlier than say 4000 years ago).
Its not my job to provide a comprehensive explanation for you, but rather to put into perspective tenuousness of the theory and these dating methods. However, it is very suspicious that these methods agree so perfectly, primarily because it is unreasonable to think that these varves are only annual varves for 50,000 years, just as it is suspicious to think that blood cells of dinosaurs can be non-fossilized and still preserved for 60 million years. Real evidence of varves and blood cells indicates that this is unreasonable.