1996 Camry P0340 and pedal malfunctions

Hi, I have a V4 1996 Camry that had a rapid, loud clicking noise (seems to
be by the timing belt and engine) when idle and it mostly went away while
accelerating. Check engine light came on about a month ago and I checked
it with a reader to find P0420 (catalyst system). Ignored it for the most part
but then my car stalled and cranked when I tried turning the engine back on.
Eventually got it to work by gassing it while cranking but the gas didn't work.
The gas revs the engine in park but doesn't do anything in drive. Pressing
the brake works but the brake pedal is much harder to press. I parked and
scanned again to see P0420 went away but now I have P0340 (Camshaft
Position Sensor). Not sure if it's a vacuum issue because the pedals,
camshaft because the scanner or something else. Any advice is greatly
appreciated. Thank you.