You might try telling your instructor that the internet access where you live is going to be unreliable for a while, so is there a place you can print it out, complete it by hand, and enter the answers only after you're finished? That's what I did, anyway. But my online homework interface had the advantage that the button to print everything out was easily accessible.
*hugs* Would you be willing to explain how the online interface is shitty? What company did it come from?
Yeah... most of those systems are designed for students in computer labs. Mobile design basically is not a consideration for them at all. This is ridiculous because mobile systems are now really important for a lot of people but a lot of these systems were designed by a committee that met in 2009. They're supposed to have some tolerance for you entering numbers in different forms but machine intelligence is just barely getting good enough to actually be tolerant enough for this stuff, and - again - as they were designed by a committee that met in 2009, none of that machine intelligence is even close to being implemented. So unfortunately I think the answer is to just not do it when you're on a phone at all.
Ahhhh. Have you considered getting a laptop, or even one of those nifty convertible tablets like Microsoft's Surface? It might get around the "I feel like I'm tied to the computer when I'm on it" problem.
