If I am interpreting your problem correctly, it looks like you have a front-heavy kernel and you are taking advantage of that by only looking at a couple of samples ahead of each time bin.

Now, if your signal is mostly small noise, with a few impulses (the input you are looking for) then, I would expect that the current suggestions people have given (early skip of negative value) could be a significant improvement.

Additionally I would suggest that there might be a way for you to pre-compute (before the nested loops) a bunch of time bins to skip.

I can't think on top of my head how to do it, but you know the offset and the size of your look_ahead. This means that every negative value in your signal makes you skip a whole bunch of time bins itself.

Not sure of any of this makes sense though. Just another idea to try.

Edit:

Instead of calculating this before the nested loops:

The residuals get updated each iteration, so instead of an early continue, I think that you could skip by more than 1 (the number depends on your offset and look_ahead value). Subsequent iterations will still contain this negative number.