Hi Anon, I'd say you could use any of your sentences. To be honest, though, I doubt I would use the present perfect in that sentence. Therefore, sentence 2 seems the most likely to me.
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Anonymous1. I will be going to work early in the morning since I have told/promised my boss that I will have been at work before 9 a.m.
2. I will be going to work early in the morning since I told/promised my boss that I would have been at work before 9 a.m.
Would here is an auxillary verb.
3. I will be going to work early