Q: HaShem gave us the ability to exercise freedom of will – making our own choices. Why, then, did he also give us guilt? Why, if one is committed to a decision (small or great), having implemented that decision, is there guilt if it turns out wrong? Does Moshe Rebeno's Torah give a viable answer?

A: In the opening chapters of Genesis, the Torah not only tells us the narrative of creation, but also insights into the world and creatures created based on the chosen language and context.
 
See below – in Chp 1:27 it states: “And G-d created man in His image, in the image of G-d He created him; male and female He created them.” By the redundancy of the language, it is evident that there are deeper meanings to be gleaned from the verse. 
 
See below – The Rosh, Rabbeinu Asher Ben Yechiel explains that it means Man was created with Divine qualities to know innately what is good and what is evil.

Therefore, I would like to posit from here that since mankind in their gut know what is good and what is evil, there is a natural feeling of guilt and a desire to correct a situation when the result of a decision seems wrong.

Rav Dessler also writes in the 3rd Volume of Michtav Meeliyahu that whatever we see in the physical world has a counterpart in the spiritual world. Therefore, just as when one is ill, there is a natural resiliency and healing built into humanity. So too spiritually, in order to provide healing, when we make poor choices we can feel guilt/shame for having done so and it can inspire us to change for the better.