Yes,Please enroll Jasper in Puppy Training,Then Obedience Class...maybe even agility after that...if you like
This will address All the issues you have described...I don't know your age...but He is Your Dog,Your Responsibility....By Shutting Him Out...Hours at a Time...You are only making matters Worse...He doesn't understand why You are Home,and He cannot be with you....
Jasper will be able to meet and Play with other dogs at these classes.....Hence,The Socialization...
Boxers are People Dogs.....They Want to Be With You!!!!
As you say...hes' getting Big...Fix these Issues Now,Before they Become a Problem that You Cannot fix....
Classes are usually very Reasonable...lots are offered at local Community centers,YMCA, or your Local Animal Shelter......

Please Keep us Updated!!!!
Jasper is a Beautiful Boy!!!!!
Learn to Enjoy & Appreciate him!!!!