Id suggest you create a field against opportunity to say if the email has been sent or not and then populate this for your existing oppo's and add a condition to your rule to only send if this field is null and then a second rule to populate the field afterwards.

This would mean the email would only send once per oppo and would stop it from sending for existing ones.

It looks like in your actions your oppo_slm_infomailsend should be set as Y not N.

Then you might one opp_status <> 'In Progress' AND oppo_updatedby <> oppo_assigneduserid as part of your condition (e.g. Opportunity is not 'live' and it was updated by someone other than the assigned person