I think the problem will be resolved. We had to have our septic sucked out once again and lo and behold, there is a third access to our septic system that we didn't know about. The full septic system isn't the problem but he told me if we've gone 14 years without having to clean out the drains, then he doubts it is a collapsed pipe. He's coming back tomorrow to do it professionally - for $125.00. That we can handle.
What complicates things, and probably why my husband couldn't clear it out himself, is because we have an "island sink" so it's not against an outside wall. He told me the longer it takes for the sink to fill up after running the water, the further down the line the clog is and it took 20 seconds for the sink to start backing up.
So hopefully tomorrow our problems will be cleared up.
That third septic access really threw my husband off, though. There's some sort of filter (called a Zaber filter) in there that needs to be cleaned every six months and it's never been cleaned. The people who have always done our septic system went out of business. Interesting they never discovered that third access. Maybe that's why they are out of business.