I think there are two parts to this discussion - one is that you'll be the one who puts food on the table and pays the mortgage for the next four years, and the pressures associated with that; the other is having the time and the will power to remain focused on sustainability.
So, you've moved to a new state, your husband is settled in university and you have a mortgage. He will be working towards gaining qualifications to improve your future lives together, while you work to support you both now and start paying off your mortgage - your future asset. You'll both have to work hard - he must pass all this subjects first time so he not paying more HECS fees than he should, you'll be working possibly six days a week. You're both living in your home, you'll have to divide the chore up to suit you both, although let me suggest that you make up a chore list that keeps everything clean and tidy and you both fed, while not going overboard on housework. Don't add more stress to your lives by trying to be perfect at home. Maybe he does the weekly shopping and the cooking and you make the bed, wash up and do the laundry. Take it in turns to clean the bathroom and vacuum. I'm sure you can work out something. Don't expect to enjoy every moment of it, it will be a hard slog, but working together for your common goals should get you through it. I worked while I did my degree and I know your job will be tougher than his, although there will be times when he'll have enormous pressure on him. There will have to be plenty of give and take and you'll both have to be flexible, generous and supportive of each other to get through.
There are plenty of things you can do to remain on your simple pathway. Don't buy expensive chemical cleaners - make up your own using vinegar, bicarb and soap. Don't buy disposables. Cut up some old towels for dishcloths, use cloth napkins, stop buying paper towels. Use cloth shopping bags and hang washing on the line instead of using a dryer. Shop at thrift shops. See if your husband can buy second hand text books or get them from the library. Use the university library to borrow novels to read instead of buying books. Use public transport. It is up to you both to save as much money as you can. Don't think it's okay to reward yourselves all the time because life is tough now. Keep your long term goals in mind and keep working towards them.
I know I've been tough but this will be a difficult few years for both of you. But if you work together as a team, focused on long term goals and not instant gratification, you'll come out the other end of this stronger as a married couple. When I look back on my marriage I can see that working together through the tough times kept us together and made us more committed to each other and to our marriage. When you see your partner working hard for your common goals, it makes you work hard too. Put in the hard yards now and you'll reap rich rewards.
Now that I can see a long life of over 60 years behind me, I know with certainty that life is not an easy walk in the park. It's a long series of highs and lows with many periods of smooth sailing in between. This is one of your first periods outside the smooth zone but what you do now will prepare you more than you know for what you'll do later. The better you cope with this, the more you'll set yourself up for success later. So knuckle down and work hard, take time out for yourself when you need it, give support when it's needed, be kind to each other and make the most of that one day a week you have off. Have breakfast in bed, take a walk and enjoy being together. The pressure is on but it can either be stress or a gift, depending on how you look at it. I know which one I'd choose. Good luck. I hope the year ahead is a good one for both of you.
The collective wisdom of the readers here never ceases to pleasantly amaze me. If you have any advice to add to help our friend, please do.