PA23 Pilot reported nose gear failed to extend completely resulted in the nose gear collapsing on landing.

Narrative

I was doing aerial imaging and had to slow down to capture one of the lines. To do so; I began to put the plane into slow flight which include extending the landing gear. After putting the gear selector in the down position; both main gear extended; but the nose gear only extended halfway; which is not far enough to lock into place. I spend about 3 hours troubleshooting; running checklists; and talking to the mechanic on the phone to try and get the gear down. After all the troubleshooting was unsuccessful; I contacted approach; [advised ATC]; and continued inbound to the airport. I did two low passes over the runway so that the controllers could examine the gear. Both times; I was told that the nose gear was not down at all; although I could see it halfway down in the mirror on the engine cowling. After myself; and ATC came to a conclusion on the gear situation; we agreed I should burn on off a good amount of fuel since I was full when I took off and only flew about 1.5 hours before returning to the airport. After burning off about 2.5 hours worth of fuel; I was vectored into the airport to land. Upon landing; I held the nose off long enough to where I was able to feather the props and shut down both engine before the nose had touched the ground. Once the aircraft came to a full stop; I shut off all the fuel; shut down the electrical equipment; shut off the magnetos and exited the aircraft unharmed while I waited for services to arrive.