I have looked everywhere in Domoticz how to reset the value(s) but i cannot find it.
As far I know, there's no way to remove only one value with Domoticz (as suggested, you can delete the sensor to destroy all values, but this may seems a bit aggressive
The way I do, when incorrect values are stored, is to modify Domoticz's database directly. As usual, you have to backup the DB before changing something, as doing it badly can just corrupt your DB, so your Domoticz (as almost everything is stored here).
Should you still want to proceed with DB changes, at your own risk, you may want to identify the sensor, stored in "DeviceStatus" table. As soon as you get the device idx (you may also find it on the Web interface), you should find the table(s) where data is store, which depends on device type. I don't have power pulse, so can't help you, but for energy meter, last day data is stored in "Meter" and historical data in "MeterCalendar". I usually change this table, either by modifying value and counter, or just deleting the row (depending on initial issue).
I've got a small Unix shell file that stops Domoticz, run a .sql file (where you have to insert your SQL orders) and restart Domoticz that I can share, on request.