How to say "No" to having everyone live in my house?

Evict everyone but your spouse. Stop running a freeloader hotel at your house.

I think the problem here is that although you keep saying no your wife keeps saying yes. If this is destroying your life to the point you are contemplating ending it then I suggest that ending your marriage is a better option. Your dream house is in reality your prison but ultimately you hold the keys - walk away and find a new life for yourself.

How to say "no"?

How about "y'all need to move out in 2 weeks".

Time grow yourself a new set of b*lls, just put your foot down and say NO, no more.

Being Christian doesn't mean you have to condescend to others and be taken advantage of.

You are being used....big time. Stop this nonsense. It is up to you, life is too short to be miserable!

The B*ll is in your court, handle this before it gets even worse....and it will....since they all know that you are weak and very codependent.

What Burnt said.

You are working 2 jobs to support able-bodied adults....while they are laughing all the way to the bank, behind your back? You let these losers use your car?
Why do I have the feeling they don't put gas in it?

Here's an idea that may wake you up:
Get a sheet of paper, make 2 columns. In one column, write down what you've done for these people. In the other column, write down what they have done for YOU.

Dont be a doormat - create a boundary and tell people it is time to leave I want my House back and My space .

You say "NO! You are not living in my house. Sorry, but NO. Not up for argument or discussion. The answer is NO".
Period.
End of sentence.

Do not take in anymore relatives , including the ill one in the hospital. She will have to be placed in a facility . And why on earth would the sister in law who just lost her daughter need to move in with you ?

Again do not take in anymore relatives . Those that are currently in your home get a 30 day notice to get out . If your wife has a problem with this try marriage counseling to have your wife see this is not fair to you . Your wife should explore with a therapist why she feels the need to take in these people .

You need to take care of you . You should speak to a therapist individually as well . If these people do not leave or your wife does not see it your way, then quietly go to a divorce lawyer to see the best steps to be free of this . It is effecting your mental health .

Just say it.

Keep saying it.

Don't give people any reasons for the "no" or they will negotiate and try to break down your boundary. You must defend it.

Just "No, I don't want anyone in my house anymore for any reason. Period. Get out in 30 days or get evicted."

Don't worry about how they'll react, what they'll think of you or where there will live after they leave. Don't accept any stalling or excuses or pity story.

Just no.

No need to make up excuses or reasons. It’s your home. “You will will to move out by next month. I’m willing to help you pack”