Have you checked the Bulbs? The Blinker bulbs also have a daytime running light feature, the running light part of the bulb can be good, and the turn signal part can be bad. I had that issue with my 97 V-6 when I first bought it.
That would be the 1st thing I would check.
When you say manually moving the lever and only the rear bulbs turn on/off is a clue. Also check for power to the front sockets. The turn signal not blinking is a symptom of a bad bulb on the old non LED systems. The bad bulb reduces the current draw for the entire turn signal system and may reduce it enough that the flasher unit does not heat up enough to make and break the contacts in the flasher unit.
If you have power to the front sockets, and the bulbs are good try a ne flasher unit.