Denali is and always has been a screamer...to the point I can't leave him in the grooming area crated at dog shows he sounds like he's being murdered...but he's always been a talker. From the moment we met him! Yet Dakota (my oldest) rarely ever made a peep until the sound of kibble hit the bowl. With Denali squirt guns and ignoring have made the screaming more manageable....it's taking time but I have faith it will stop, as he is maturing it's lessening as well.
With the potty training, keep him on lead and about every hour walk to the same door, exit, and give a "go potty" type command. When successful potty happens special treat that he only gets outside...eventually he will associate that door with having to potty and go there when he needs out.
Aggressive/Possessive needs to be taught Drop It or Leave It...that will save your hands and when he starts getting edgy with others around his treats/toys giving that command will let him know that he is out of line. An appropriate training program should be enough to correct this issue.
Good luck with everything! And most importantly be patient and consistent