@Andi Morgan, you have so many things going on here I don't have time to address them all.
First LLCs are not magic, but they work very well if you set them up and use them them correctly. Yes you can be sued personally anyway, but more often than not they are dismissed in a Motion for Summary Judgement. When a state makes a law saying we are giving this kind of protection judges are obligated to follow the law. There are lots of exceptions, just like how a Dr. treats an injury, they do it like this, unless this happens, or like this if that happens, etc. They do work, but are not silver bullets. I was legally sued by a little old lady because I dismissed the criminal charges against her spraying a guy with mace, then hitting him with a taser. I met the "victim" and I wanted to mace him after a two minute conversation. I had to answer that lawsuit, but the judge dismissed it for a lot of reasons.
You do have problems about how to file your tax returns if you start joining your significant other into existing single member LLCs. All of the same stuff is still put down, but it is on separate filings, not as a schedule, C, D, on your personal 1040. That is an accountant issue you need to work out. What you really need are excellent operating agreements. It is great you are sharing life and finances with another, but what happens when one of you decide to love someone else, or what if one of you goes bankrupt, or even dies? Their children or brothers and sisters may now become your partner, and they don't love you. they just want all the money they can get. You really need things to say what happens when one partner wants out or one dies. How do you set the sellout price? How long do you get to set up a loan to buy them? Who handles the day to day decisions on buying or selling a property if you cannot agree? Are you forever deadlocked? Those should be decided before you add the significant other. Once you add them into the LLC you are married in a very real sense, financially. Hopefully you worked those things out long ago, if not good luck. Resolve while you are still in love. There may never be a problem, but the odds are very high that it could. Either way I wish you good luck and happiness.