"Material Change" and Duration of Spousal Support

I will say in advance, that I do have a lawyer in Alberta but I don't feel he is representing my interests but I have no way of knowing, further, I can't afford to keep paying him to tell me about all her rights and not explaining to me about mine. I also can't afford to fire him, and pay another retainer fee to someone else so I am reaching out in forums to find some answers or guidance. I am in the process of completing a separation agreement with my wife to finalize our divorce. I was in the Canadian Armed Forces (CAF) for 12 years but I'm not anymore. We have already agreed on division of finances, division of property, she has half my pension and the cost of spousal support. What we cannot agree on is what her and her lawyer are trying to force in to writing as what material change can and cannot be as well as the duration of spousal support. My concern is that her and her lawyer want it stated explicitly that since I quit the CAF that it can't be considered material change for the purposes or reduction or cancellation of arrears. My lawyer tells me that its the law anyways so I should just agree to it. However, If I agree to that language in the separation agreement, that to me says that no matter what happens to me in the future, new job, better job, worse job, legs cut off, etc... I will still have to pay, because I agreed that I left the CAF and that I can no longer as for a reduction or cancellation. Is this true? Or am I reading to much into it? The way I read the law is that my spousal support is based on my income, and I would rather the court decide that than her lawyer forcing me into a corner. Any advice? Also with the length of payment, my wife is 47 years old, she did have an accident years ago in a factory but she was pensioned off by WSIB and then fully retrained at an educational facility and program of her choice, and then has proven she can succeed and be gainfully employed in that field, further, she ha been trained in in medical office Admin and banking, both of which she has held successful employment in. Now she claims she can only find part time work in a bank , Mon, Tues, and Thursdays only. She has plenty of training and experience and time left in her career to support and better herself, why should I have to continue paying her for ever? Any advice?