Does a chain of probabilities still indicate rational choice?

Hello Rabbi Michael,
 
As I understand it, your course of faith is this: It is likely that there is a God (in light of various arguments). Given that he exists (and in light of several other data) it is likely that he has been discovered. In other words, there are two arguments of probability here that ride on top of each other. Now, I know that there is a certain problem in quantifying this, but to clarify my question I will give these probabilities numbers.
 
Let's say, a – there is a God. Chance: 60%.
And: b- God has revealed himself. The chance – *given a* – is 70%.
 
It can be seen that even though each step along the way is plausible (i.e., most of the chances are in favor of it), it still turns out that the chance that b happened is 42% (0.6*0.7). That is, most of the chances that b did not happen. So it is seemingly irrational to believe in this scenario – despite the likelihood of each step.
 
On the other hand, it can be said that it is the most likely scenario (only a and not b – 18% chance. Not a – 40% chance). So it can be argued that it is still rational to believe in b. But in our case there is no practical difference between "only a and not b" ​​and "not a" – because in both cases God has not revealed himself and therefore there is no obligation to keep the commandments. Therefore, it is correct to examine this from the perspective of what is the chance that b is true in itself and not what is the most likely scenario among the options. And so it turns out that belief in revelation is irrational, even if each step in the chain is reasonable.
 
I would love to hear your opinion. Since you ultimately claim that keeping the commandments is the rational choice, I assume that: either you disagree with this analysis, or that in your opinion "the percentages are higher" (even if this is intuitive and cannot really be quantified like this. The numbers are just to clarify the point). I would love to hear which of the two options you think.
 
thanks!