The rules state that if a player is pulled back outside the area but the offence carries on into the area then a penalty is the correct decision.
Dowd was correct in the pen and red card. The defender comittied the red card offence, Dowd played on to see if Wickham could go onto score, he didn't and you have to take into the consideration he was pulled back which had an influence on that. Dowd then took it back for the pen and red card.
If Wickham had scored after the advantage i do believe the defender would not have been shown a red.