Can I fix medium sized crack in windshield or do I have to replace it.

That is major damage that is going to continue to grow. If you simply push on the glass with your thumb, you'll see the crack grow longer right before your eyes. The glass actually flexes a little each time you hit a small bump or drive over uneven road surfaces. That flexing is what has already caused all those long cracks.

The only time a crack can be repaired is when the damage is about the diameter of a pencil eraser and there's no cracks extending out yet. The repair must be done by a professional with very specialized equipment. He installs a suction cup, then uses a pump to such the crack into a vacuum for about 20 minutes, The vacuum causes water to boil at 77 degrees F. And get drawn out, then a special resin is injected into the damage. That glue prevents cracks from starting as the glass flexes.

Typically this repair costs around $50.00, and the repairman comes to where your car will be parked for an hour. You don't have to go to his shop.

The location isn't the issue. I've watched these guys perform repairs in the middle and near the edge, but in all cases they're repairing small chips that COULD turn into a run. The resin keeps water out that could freeze and expand, and it prevent a run from forming. Runs can't be controlled, and you have over a dozen of them already. There's absolutely no question this damage is way beyond repair. Most companies will tell you a half-inch chip with no runs, or cracks, is the largest they can repair. Your runs are about three times the size of the suction cup they use. Sorry for the bad news, but you'll also be surprised at how quickly they can replace your windshield. They'll come to you for that job too and will be gone in less than an hour.