All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
Indeed your question included different matters:
The first matter:
The ruling about your company failing to keep its promise of increasing your salary depends on the type of contract which both of you (the two parties) had signed. If increasing your salary is one of the terms of the contract (even if it was orally agreed on) then the company has to fulfil this requirement. But if it is just a promise and that is not included as a term in the contract, then it does not have to fulfil it, but it is desirable for it to do so.
The second matter:
The ruling about your loan with interest: There is no doubt that by borrowing money with interest you have indeed committed a great sin. Therefore, you have to repent to Allaah for committing such a major sin. If you can repay the money you owe without the interest, do so even if you have to deceive them to avoid the interest. But it is not permissible for you to run away from repaying the sum you originally borrowed (before interest). The fact that your company failed to fulfil its promise or was neglectful about your rights does not make your failure to repay your debt to the bank permissible, as these are two different matters.
The third matter:
The ruling of running away from your company without their permission: This again depends on the contract which was signed between both parties. If you failed to fulfil the terms of the contract, then that is forbidden and you have to return to the company in order to fulfil your obligation under the contract but if you did not fail to fulfil the conditions of the contract, then there is no harm on you.
Allaah knows best.