Frame is fucked, you would be so stupid to try and ride that on the road now, I can't believe you are even asking the question. Not only will the head tube angle be a lot steeper making steering fucked and toe overlap a massive issue it WILL fail at some stage, maybe no straight away but it at soon and possibly in a very nasty way. Putting a front brake on that frame will actually do more harm as using the front wheel to stop (as you found out) puts large rotational forces through the head tube, doesn't matter if your using your foot or a brake the loading is similar. Bin the frame, get something else and put some brakes on before you go riding.
Frame is fucked, you would be so stupid to try and ride that on the road now, I can't believe you are even asking the question. Not only will the head tube angle be a lot steeper making steering fucked and toe overlap a massive issue it WILL fail at some stage, maybe no straight away but it at soon and possibly in a very nasty way. Putting a front brake on that frame will actually do more harm as using the front wheel to stop (as you found out) puts large rotational forces through the head tube, doesn't matter if your using your foot or a brake the loading is similar. Bin the frame, get something else and put some brakes on before you go riding.