Wondering how I can help my pup through a chaotic time for both of us

I'm a student, and I've had my dog for a a little over 6 months now. He's a 1.5 year old Rat Terrier mix that we got from a local shelter.

I am aware that purchasing a dog as a student usually isn't the best decision, but there were a few key things that made me more comfortable with the decision.

1. I am about to graduate, and I have a job lined up for after then. I've managed to tailor my final semesters to be very low time/class commitment to have more time to take care of him and work part time.

2. I wasn't adopting him alone. I adopted him with my at the time roommate. We talked about it extensively ahead of time, agreeing to split costs and labor. We got along very well, and had had no major issues for the 2+ years that we had been living together. We knew that we would likely be parting ways in the next couple years, and agreed ahead of time that whoever took him at that point would pay the other person their half of the adoption fee and pet deposit. Around early January, we ended up deciding that I would take him whenever that time came.

3. We live in a house with a large yard. I wouldn't have dreamed of adopting a dog under my present situation if we lived in a small apartment. Our house isn't huge, but it's enough room for us and our other roommate, and our yard is about 1.5x the size of our house and fenced in.

HOWEVER, less than a month ago things fell apart with my roommate very suddenly and they announced they'd be moving out at the end of February. Also, I'm defending my senior thesis next week and my defense copy is due in a couple of days. This has left me unexpectedly with full custody of our dog during a time when my schedule is completely fucked.

When I'm not working or in class, I'm working on my thesis. As soon as the defense copy is submitted, I'll be preparing my presentation. Our typical routine is essentially non existent. I'm doing my best to get him outside, exercised, and stimulated. I've made him a bunch of puzzle toys for when I'm working, and when the weather's good I work outside so he can play in the yard (he doesn't do well in the yard alone for long periods of time. It's something we've been working in terms of building his independence, but that has been thrown way off along with the rest of our routine). Before, I had someone else who could walk him half the time and also give him attention when he needed it. Now it's just me, and it's clear that I'm not meeting his attention needs right now.

I don't know what to do. In two weeks, I will be able to fully commit my time to him, but right now I just can't do that. I had gone into this project under the impression I'd have backup, and now I'm alone and worried and feeling guilty for my pup. He's healthy and happy overall, but he deserves so much better and it's also taking every last ounce of energy I have.

If anybody has guidance or advice, we'd both be very grateful.