We have 800fico, 950Khouse, owe 216K-30yr. loan @ 5.5 but have dumped additional 30K-loan is 7years old, 1619/mo payment

800fico, no debt, golden! Good income, but college daughter off to school next year. Options are a no cost 15yr. fxd. @ 4.25, same payment but will need 70K over 4 yrs. to fund her college; 5/1arm at 900/mo. payment w (3000 out of pocket) and sends me back to 30 yr. amort. schedule-mostly interest; just doesn't feel right. ; other way is to get 15yr. fxd. 4.25, no cost, same payment as current only 40% more going toward principal-yippee-grab a free heloc and pay for college with it. Problem is that's a stretch on my income. I have 125K cash also but would like to keep that much liquid.. Any ideas? Hate the thought of going back to a 30 yr. amort. schedule but not sure I can fund needed college costs with current income unless I tap into cash savings. Also have 80K in 529 plan. 59 years old-I don't want to work forever. Someone help me figure this out.