I had my second lower molar removed five days ago. I went for a follow up for the pain and the dentist removed the stitches on the fourth day. Are four days long enough for healing? Will the blood clot be ok?

No Problem! Stitches are placed to prevent wound open more than it should.Also to "stabilize" the blood clot so to prevent abnormal bleeding. If you are not bleeding or in pain, there in nothing to worry about. On the contrary, in your case is better sooner than latter to have them removed. Usually stitches are removed after the fourth or fifth day to prevent infection due to food debris trapped on stitches.
4 days is short. When we place stitches we generally like to remove them about 5 days later, long enough time for the healing process to start, and short enough to prevent new growing gum cells from migrating down the suture track which causes complication later. Ask you dentist about this.
Suture removal. Yes you will be fine. Usually it takes 24hrs for a blood clot to be stable. In four days, healing has already progressed and there is no harm in removing sutures then . As long as you have no severe pain or any other symptoms of infection, you are fine.
Stitches not necess. Sutures or stitches are not always needed for healing. If the dentist felt comfortable removing them, then it is likely that the extraction site will be fine. Obviously, if you have future problems, contact your dentist again.