Wore out three sets of tires already!
Yes, you should add a front brake. A front brake works much better than a rear brake and adds redundancy. You can either drill your fork as recommended by 49autocycledeluxe or swap out the fork as recommended by SchwinnFinn63. I have used both approaches. In your photos, your fork looks quite drillable. The spot to drill would be where there is a small slot. First two photos below show a bike that I drilled. Third photo shows a couple of styles of forks that could be swapped in. Finding a donor bike shouldn't be hard, but remember that you have to match for wheel diameter, steering tube diameter, and steering tube length. Have fun!