Think hard about it. The approach is not a purely legal thing, it is a practical navigation instruction. Ask yourself the question "Can I properly follow the navigation instructions?" If so, you are "legal".
If you defined the step-down point with a valid DME, then you have properly navigated to it, and possibly do not require climbing back up to the higher mins. The one case where you might be in trouble is if the MAP were also defined by DME for that lower altitude. If this is the case, then climb back up. If you can execute the published procedure from 380 step-down onward without needing a DME, press on.
Unless specifically allowed, I believe the GPS does not replace a DME for the approach. Is the approach a GPS/LDA?
The RVR conversions allow you to decode the reported Wx with the approach RVR. The conversions are not precise, and not allow mix and match.