How often is "too often" for emailing journal editors?
As you point out, you've waited close to a year. You shouldn't feel bad about asking for updates after this long, especially since it's been two months since you last checked.

In your email I'd point out that it's been almost a year since you resubmitted, and you're wondering what exactly is happening. When can you expect a decision? If they can't predict that, then when are the reviews due?

If the editorial board member handling your paper is unresponsive, you could try asking the journal office instead, although it sounds unlikely the journal office will be able to say much (because my guess is the reviewers never agreed to review and/or never actually submitted a review, so the only way forward is to invite more reviewers, but the handling editor hasn't done it).