When you are served with the divorce complaint you will have 30 days to respond.
I suggest that if YOU think the problems pointed out by the second attorney are indeed issues that you can not live with, then take the agreement back to the first attorney and address these issues. Find out if that attorney also sees a problem with these things.
If you do not trust the second attorney is qualified of looking out for your best interest, and do not feel comfortable going back to the first attorney, then yes you should consult a 3rd. Have the separation agreement and the divorce complaint looked at. Find out if there is anything that can be done to respond to the divorce complaint about renegotiating the terms of the separation agreement or at least that it will be decided at a later date, so that time doesn’t run out…
I would also mention that if you signed the agreement then there may be little if nothing that can be done at this point.