Could your father have been an Aries Sun as well? In my case, my dad is a Libra Sun and so am I. Sun is my PiK as well. Just thought I'd throw this out there.
I wonder if it could be interpreted as follows -
We get what we are. The darkness of Rahu with Mercury in 10th created a shadowy figure of what a father figure or a role model would be like. With Mercury there, you don’t have the opportunity to see the details of it either through different people.
10th house is also about taking care of our material well-being, so I am assuming you had to figure out ways to do that yourself, and your exalted Sun would have helped. Your mother encouraged you, denoting Ketu in 4th - what you already knew.
If you had had a role model, you would not have had Rahu in 10th house, or it would have been a different kind of situation where you would still have to find out about yourself in terms of the 10th house.
This is an interest question because i have a chart where the individual has a great father, a good 10th cusp yet the Sun in the Rasi is mediocre. I think a planet represents many things, many aspects of our lives like the vargas. A planet could be exalted in one varga and debilitated in another. The Sun is father but it is also you and your path. You have an exalted Sun, and i think that shows that you have always known your path. You have always been strong in following your own path. That is why astrology is so fascinating in that you have to look at many clues to derive at a conclusion. I don't think a bad or a good father equates to a bad or good Sun necessarily just because the Sun is the Karaka for father. Sometime the Sun represents father, and sometime it does not in a chart... Sounds like the Sun here represents you more than your father...
tuyet
I wonder if there was something exalted about your father, something noble that went wrong in putting it into practice and relating to the world. I have a similar combination of good dignity and yet hammered situation in respect to planets relating to 10th house and father karakas and I can say from my experience (father is still alive) that my father has had very noble and exalted aspiration and goals, but in carrying them out things did not go as planned and how he reacted to them is reflected by the darker aspects surrounding 10th house factors in my chart. This has reflected very clearly in my own path of working to not succumb to the same influences that caused the erosion of my father's more noble side. The mystery will become more clear through the Dwadasamsa.