Dashboard lights dim even when switch is OFF.

Hey guys, I am new to the forum so I apologize if I posted my thread where it shouldn't.

Okay so I have a 04' Skoda Fabia Classic 1.4 MPi, 8V. She's my first car...

When I get in the car the first thing I see is the Fuel Reserve light not bright like if it was ON but really dim even with the keys out. It's weird because the battery hasn't drain in over 3 months... How can this be solved?

Also, I am doing an engine overhaul (sealing everything, changing head gaskets, oil, filters, timing chain etc) so my car has a slim smell of fuel...is the fuel filter going to fix this?

Last thing (so far) I got the P0170 error about fuel/air mix too rich on bank 1... Have NO clue about this.

Thanks in advance!