A quite worn front tire can make the front seem slow compared to the feel with new rubber, but it's not so bad that it would make the bike not turn. There would have to be something seriously wrong for a bike to do that - if the rider input was normal.
When you brake hard (With the front brake) do the headstock bearings make a noise? They shouldn't be too tight, but not too loose either. Just enough to have no play in the bearings, but if they're worn - then they can be notchy.
Anyways, if tyres are properly inflated then it's probably rider error. Perhaps ask someone who is used to riding big bikes to take it for a ride and check to let you know what they find it feels like?
Euro RC51 SP2: HRC WSB Ti Hi-Level, T1 Airbox & Snorkel, PCIII, Dymag CA5 Carbon Wheels, Ti64 Spindles (F, R & Swing Arm), Mori Link, Maxton GP7 Shock & Ohlins 832 Forks, Brembo GP Calipers & SBK narrow track (F), Braketech Disc (R), Brembo billet Underslung x 2 Brembo RCS, Tyga Triple, 7075 Stem, Probolt Titanium all over, Babyface rearsets, MR Complete Carbon Lineup, Custom Undertail & CBR 1000 LED, Watsen LED Indicators, Harris Brace, Giles clip-ons, Corbin seat, etc. 2013 BOTY.