Termination order can be stigmatic. Dismissal can mar the employability and employment opportunities and options.
This is the precisely the reason you feel that you no other option but to sign on the dotted line.
Would you feel that it shall be appropriate this time to discuss {on record} that how does the company arrive at a figure of 3.00 Lakh and 3 years, and justify it?
What was the actual cost incurred on you for 20 days training last time? Do you have itemized detail of all expenses? Was it actually a training that added to your special skills and qualification? Or was it a training that was unavoidable for the company to run its say machine?
You should keep all record so that at a given point of time and in appropriate forum you are able to defend you if required.
There should not be a situation under which an employee is ordered that he should undergo the training, sign the bond of figures decided arbitrarily by employer or he shall have to fall under the axe and face dismissal.
Once you sign employer shall claim you signed by your free will and it shall give him the right to claim as per contract and even initiate process of notices, legal notices, litigation.
The lawyer of employer and employee shall do their level best to defend the interest of their clients.
However courts shall take an informed view of the situation and take a qualified decision.
Court may feel that the visit claimed as being training was no training or for that matter training did not add to qualification or skill of the employee and company was under obligation to impart such training at its cost or the amount being claimed by employer is not reasonable and may fix a reasonable amount and then ask to apply the formulae of 100%, 50% and 30% as mentioned by you.
You may find the attachments useful.
It shall be appropriate to show your appointment letter, HR policy, employee/service rule book, and standing orders of the company, bond old and new to a competent and experienced labor consultant/service lawyer and give inputs in person. The bond may be in violation of the standing orders of the company.