Machinist’s trick....get another 10mm nut that fits on the stud...run the new nut down to the old nut...tighten the two nuts against each other, locking both onto the stud...this will give you leverage on the nuts to back or pull the stud out.
I’d try the two but trick. Btw, it’s not a sending unit. These engines are notorious for sludge. Do a Google search for it. You’ll get good at dropping the pan and cleaning the oil pickup before you sort it out. Run Wal-Mart conventional oil with 20% marvel mystery oil and change every 3k. You might also pull the oil press sender and clean it. A full de-sludge is no job for amateurs, but a gradual cleaning should get you by.
This. Run another nut onto the stud and unscrew them together. If that doesn’t work, quit jerking around and take it to a Toyota dealer.