Rainey - That's a really good question, and some of the answers are outside of my area of expertise, but I suspect others on this forum will have some thoughts for you.
Strictly from a CPP perspective, you should be aware that the retirement pension estimates from the Service Canada site assume that the next 23 years of your working will be identical to what you've earned between age 18 and now, as compared to the YMPE for each year. If you don't contribute any more to the CPP, your actual benefits at age 60, 65 and 70 would likely decrease by about 50%, since you're 24 years into your contributory period and you've got 23 years left until age 65. I could do some actual calculations for you if you emailed your CPP statement of contributions to me at
DRpensions@shaw.ca, but I charge $25 for each accurate calculation.
On the other hand, what your current contributions will "buy" you in 23 years is probably irrelevant to your current decision. A quick way of looking at payback on CPP contributions for a self-employed person (9.9%) versus the retirement benefit value (approx 0.64% per year of contribution, at age 65). This would give you a breakeven period of approx 15.5 yrs after you become eligible for an age-65 retirement benefit.
It's flawed to look at CPP "value" just on the basis of retirement pension payback though, as the CPP also covers you for disability and survivor benefits. Disability benefits require that you've made contributions in at least 4 of the last 6 years prior to becoming disabled. That means that if you decide not to contribute to CPP, you may want to take out your own private disability coverage, just in case.
I don't know if any of this helps, but good luck in whatever option you choose.