paying back the bond
For me there is no problem with leaving an employer - you sign a contract agreeing to give - say - three month's notice. That's all you need to give and, however good it is there, the other posters who've said the company would not hesitate to make you redundant if it needed to are right. It would be a mistake to give them more loyalty than they give an employee.
The bond does complicate things. FlyMD has the best idea. Be straight with the guys if you can't pay it off and try to come to an amicable arrangement which might consist of paying a reduced amount or by installments. If they aren't interested it might be worth taking legal advice as I doubt they can take you to court immediately for non payment if you have agreed (say) to pay over time.
The problem with running away from the bond is you might end up with a criminal record and then, however unfair it might seem, you would not be able to get airside clearance. With no airside clearance.... no pilot job.