I have many questions here, but ultimately they don't matter because you're 20, tall, and underweight. You can do the plan you mention and see how it works. You might need more calories at some point, but you'll find out soon enough.
As far as things to reconsider, I would suggest that if at age 20 you think you may be too busy to find time to train consistently that you re-evaluate how you prioritize your time.