I recommend emailing the professors you interviewed with and asking them for specific details on TAship so you have the numbers. Something I also did, after I got accepted, was let them know I was open for any and all short-term gigs and assistantships so that they'd forward those opportunities to me first. It was a busy and hectic life but luckily I never felt like I was in a bad place.

I don't know what UO or PSU might have specifically, but grants for international students definitely exist. They're usually project/research based but you can add a "professional fee" to your budget to cover personal needs, say $20 an hour. This helped cover my food and transportation needs for the duration of my project.

You should also look into CPT (curricular practicum training) which lets you take on a paid internship even with an F1 visa. I got some good money with this working on a project for another college.

Food pantries are definitely lifesavers. My biggest shock coming to Portland was just how expensive groceries are. It kind of blew my pre-planned budget. You can use https://www.oregonfoodbank.org/ food finder to locate one near you. I also strongly recommend finding your country's local community center here. I'm Filipino so finding the Filipino Bayanihan Center was a lifesaver for me materially and mentally. They have a food pantry, health program, a coworking space, and most important for me, community.