For the dodgy reading on the fuel gauge check the lift pump connections. Been through any floods at any time?
Lift the rear seat bench. Lift the carpet flap on the drivers side. Remove the 3 posi screws and inspect the top of the fuel pump for silt and general contamination.
Refresh the electrical connection and spray with WD40 maybe. I've advised frodrizzle about this when he resurrected a flood damaged Anni. Fixed his erratic fuel gauge 

Golf Mk4 | Satin silver | K03s | Rtech 231 bhp stage 2 | Blueflame turbo back | BBS RCs | Coilovers | Eibach F&R ARBs | K&N panel | SFS TIP | W8 Interior light | Girlfriend drives it
Golf Mk5 Edition 30 | Steel grey | Manual | Xenons | Lux pack 2 | Armrest | Highline