So did the 5v psu make a difference to the spikes?
The led not flashing is due to the firmware (incorrectly) assuming you are running on batteries when the a.c. signal is missing (to extend batt life). If/when you remove the internal a.c. link the led should flash again.
The pulsecount will always reset at power up, when the reset line is gnd’d or at rollover, this is expected and emoncms whaccumulator processing is designed for such behaviour.
The 0 temp values at start up are not ideal and this is a known issue on both the emonth and emontx units.
If using a 5v psu to provide a more stable 3.3v to your temp sensors (via the 3.3v screw term) has not resolved the spikes entirely, try moving the temp sensor power wire to the 5v term (only at 5v when 5v psu used, not via AC or batt). This combats the DC voltage loss in the thin wires and long runs to the ds18b20s, I always power my ds18b20’s at 5v even when the data wire goes to a 3.3v (non 5v safe) io pin, this seems to be more reliable and has never caused any damage for me.
If I recall correctly, the pulse counter and temp sensors are powered by 5v on the emonpi via the rj45.