8 weeks severance after 15 years is exceedingly low and a court would order more.
That is because you would be entitled to more than the minimum about set by the Act.
A court would say that you are entitled to receive reasonable notice or pay in lieu of notice.
Generally, in determining what is reasonable notice Courts look at several factors including the length of time you worked for the employer, your age, your position, the likelihood of finding new employment etc.
At the high end, if you were in a managerial position, the Court would likely order one month's notice or pay in lieu of notice for each year of employment. If you were not in a managerial position the Court would order somewhat less.
And the ROE is simply wrong. You were not dismissed for just cause and so it has to be corrected so that you can get EI.
For these reasons I suggest that you consult with an employment lawyer face to face as your next step.
Let me know if you need any further clarification.