I would add a little white wine to the mix.

Harissa is especially good with butter, so I'd probably melt butter and mix the harissa into that, then spread it over. Possibly with a dash of honey, though I usually tend more toward the harissa-butter-lemon juice end. Salmon is a fairly sweet fish as it is, so you may not want the added sweetness of honey.

I agree with phyllis. The honey might burn if you only use honey. Thin with olive oil, and maybe a splash of lemon juice. The sweet with the heat will be nice - especially on salmon.

I would thin out with olive oil and also add a little honey. Slather on and cook. Yum.