I don't think you'll be able to persuade your spouse on risk information
You may develop health problems in the future, or not
Unfortunately, there's been relatively little interest in accurately assessing the risks for cigar smoking [see NCI monograph], so it's mostly guess work
However, it's clear there isn't any "safe" tobacco product [& the nicotine replacement products may also pose risks] (There's also no zero risk in being a non-smoker, so epidemiologists speak in terms of relative risks, the fraction increase relative to the lowest known risk)
Your particular individual risk would be tricky to estimate, but if you've smoked cigarettes heavily for many years, switching to cigars wouldn't necessarily have reduced your risks from that exposure substantially
Here's two postings you might read:
http://www.cigargroup.com/faq/health/ncifaq.htm
http://www.cigargroup.com/faq/health/