I don't think they can make you sign a binding contract for PNP but talk to a lawyer or talk to the BC ministry of education and labour market, they govern over the immigration policy and might be able to help you, their contact at http://www.gov.bc.ca/aved/contacts.html You can also talk to the BC PNP at http://www.aved.gov.bc.ca/provincialnominee/strategicoccupations/contact.htm
The general rule about PNP is that you can not force your employer to nominate you and your employer can withdraw the nomination at any time. I do however not believe that they can use it to their advantage and make you sign a 5 year contract but if you find out that they can't and you say that, then they might not nominate you at all. If you want to go for PNP, you have to decide if you want to push for PNP through this company, even sign a 5 year contract if you have already found out it's illegal and will not stick or if you want to look for another employer and do PNP with them.
You can apply for FSW if you have enough points. If your only skilled work experience is as a manager by this employer in Canada and your work permit does not say manager but something else, you will need a letter from the employer to prove what you have been doing. You can apply for CEC after 2 years working in a skilled job and again, you would have to prove that. You still need the employer to co-operate with you so play nice.