Another Starting issue

[applecrisp]

So ill say first off yes I did search and read quite a few posts nothing quite suits my issue..

So, got in my car drove to work and noticed gas gauge was all over the place empty then full then half the empty.. but car started and ran fine.

got off work and car would not start but all dash lights and radio came on fine..

when I turn the key there is no cranking no clicking no nothing all I hear is the single deep click of I believe the throttle body.

tried a jump start with cables, no different still no crank or start.

tried a push start about 4 times for sure fast enough and would not start. so I towed it home.. I am thinking either starter relay, ignition switch, ECU or clutch safety switch.. however is it possible it is the immobilizer ?

finally where are, and how do I test the above mentioned things.