99 Civic LX will not crank

A quick explanation as to what happened, and what I've done since. A few
days ago I noticed my engine was ticking badly from the top end so I
checked the oil to find it was severely low, I refilled the oil with fresh 5w-30
and it continued to drive fine but the tick was still there so it was suggested I
put in some of that lucas oil stuff which helped greatly. A few days later while
returning home from some errands my car just died. No warning, nothing out
of the ordinary, it just stopped. I had the car towed home, and noticed the
battery was fairly low so I replaced it. I tried firing up the car again but all I
got was a couple "ticks" (from the starter) and nothing. I thought maybe the
starter was faulty so I replaced that too, no good, same problem. I have tried
to manually turn the engine via a socket + extension through the wheel well
and it will not budge. I should mention I own a code reader and there's
absolutely nothing reported wrong through the sensors so it has to be
something mechanical that the car has no sensor for.

It's been very cold out with snow yesterday so I was wondering if too much
of that oil additive could cause the pistons to stick but that seems like wishful
thinking. So I guess my question is, is there anything else I can try? Is my
motor shot? And what could have caused it? Any help would be appreciated.

Thanks.