I wouldn't use 'I have told', just 'I told'.
That simplifies the rest - you are now considering what you told them & when.
The action was all in the past, so you could use 'had'.
However, at the moment you told them in the past, it would be the present, therefore 'have' as a future perspective would be valid.
The difference is how you feel you are reporting it. Are you reporting an entire event in the past; or recalling that, at the time you told them, it was the present?
In practise, now you have eliminated the confusing have & have/had in the same sentence, no-one would care which you used.
They wouldn't really need to differentiate between you reporting the past action from a perspective of now, or whether the entire thought was cast back to the past.
I'm no grammarian, but I can't really decide if it even is a remote conditional. It doesn't really have a condition, or I'm not seeing it. Clarification from someone smarter than me may be useful ;)