renege on pan plan after task accomplished

I have worked for my company for many years and have worked in many departments. In late 2006, I accepted a position in the sales dept signing an agreement of salary and commissions to be paid. After several favorable reviews and several bid participations with clients on potential new business, our company has been awarded a rather large bid that we are currently working on closing. Recently, I was told that due to my boss's position being eliminated, that my company wanted to demote me and place my boss in my position, I would continue to work on same accounts, but only receive a small portion of the bid work that I had worked so hard on. When I refused to accept, my employer then offered my same position, but with a change in pay plan which would reduce my potential earnings by 30%. Is this legal for employers to do? Make false promises and renege when work is accomplished. If I do not accept, will I be eligible for unemployment? Employer wants me to stay, do same work, travel on personal time be on call 24/7 and not hire any help as previously agreed, all for less money. Do I have any rights or does employer hold all the cards and I am at their mercy?