If we see the closing ranks for the Computer Science and Engineering branch at the Indian Institute of Technology Bombay for the Schedule Cast category over the past few years, then the statistics are as follows:

2021: 28
2020: 29
2019: 21

So, getting a rank in the SC quota between 20 to 30 can be a safe margin and unfortunately IITs don't offer any reservation on the basis of parental occupation. Hope I have answered your question. All the best

In 2021, for a Scheduled Tribe candidate to get Computer Science and Engineering at the Indian Institute of Technology Bombay in a gender neutral seat you had to get an ST rank of 11. The trend of the rank has not changed over the years and you may expect the getting a rank of 10 is a safe score to get IITB CSE seat.

And no, you won't get any benefit of your father serving in the Army as IITs in general do not any reserved seats for such categories. Hope I have answered your question. All the best!