My question is: Is now a EDTO dispatch required to fly these routes if weather is marginal over these airports?
Could be these airports be considered as ERAs even if forecast weather is very poor?
Adequate is still in the EDTO rules. Technically if all the airports on your route are adequate for type of aircraft (Length, strength, approach and RFS) and within 60min still air single engine then you don't need EDTO and don't need to have ERA that have weather above en-route minimums. Maybe not smart but legal.
The major difference (apart from the fire suppression and fuel requirements) between ETOPS and EDTO is the definition requirement of an entry/exit point. ETOPs the flight was ETOPs from takeoff until landing, EDTO the operator must define an entry point and an exit point. i.e. the first time the flight is beyond 60 min and when the flight can remain within 60 minutes until landing. Within the entry/exit the flight must have "filed ERA" and monitoring of the weather and airport availability and a fuel quantity sufficient to divert in the worst case i.e. 1EO or DP or 1EO and DP.
In answer to your second question you can divert to where ever you like, it does not have to be a filed ERA.