I am a salaried employee and am entitled to 2 weeks. Vacation and 5 personal/sick days. I am required to work overtime without pay.
I recent just came off an illness in which I missed 12 of my 15 vac./personal days.
I was told I could lose those days, or not take the pay. However, I will have more than made up for these lost hours this year. It seems to me that my employer is wanting his cake and eat it too. Is this legal? How can I approach this with him if it isn't?

Somehow in your mind you think that working overtime and not getting paid means that you are entitled to those hours you worked with pay. Being a salaried employee means that regardless of how many hours a week you work you are paid a set amount. I think a two week vacation and 5 personal/sick days a year is quite generous. I would either take the pay or leave the days intact. It is you, my dear, who wants to have their cake and eat it too. No, your employer is well within his legal rights to ask you to do this. Remember, there are lots of other people out there who would just love to have a job these days so you should be pretty easy to replace if you decide to "fight" this out with your employer. Remember, they can fire you for any and no reason or simply lay you off. It's an employer's market out there, not an employee's market. Please keep this in mind.

You are an exempt employee, where this is no overtime. I am positive you were aware of this before you started. You need to stop counting your "overtime" or find another job. As far as the rest, I think I read this as you were sick for 12 days? If so you either take it as time off not paid or use up your vacation/sick days. He is not breaking any laws by requiring you to do so.

As a salaried employee there is no counting the hours, heavens, at 60 plus hours a week on my shortest week, I guess I could add up 20 weeks a year "extra" time, but that is just part of being salary, But normally it also means that you will get paid if you are not there also. But for days off they can ask you to use your vacation and sick days first, but after these are gone, this is where the issue will happen, if you have to take off sick again and miss work, as a salary they may not be able to take pay away for valid sick time.

I will say that all my employers (well.. my department heads, actually) have been pretty understanding about "comp time". In other words, if someone who was salaried felt bad, or needed to take time off for a day because they had the flu, or needed to take off for an hour or two to run an errand/doctor's appointment, etc. they would let the person do so with the assumption that the time would be made up at some point and the work would get done. However, there is no way that they would do that for a 12-day absence. And every company I have worked at has required that someone who is ill use sick days, vacation days, and then the short-term disability would kick in.