English Springer Spaniel

I have a 7 month old springer that was given to me as the previous owner was allergic to him,although i am now thinking this was made up and that he could not cope with him. He is such a handsome dog and very loveable but such hard work and needs your attention constantly. The problems i have is that he is not fully housetrained and does his business indoors and out,hates his cage and being left alone,will bark and howl when put in there for just a few moments. He is very aggressive around food and shows his teeth if we go near him when eating,barks and growls at strangers which is a great concern. He tends to get very bored and will tear up or destroy almost anything although not the furniture. I have taken him to 2 dog trainers who totally contradicted one another,spent hours on the internet looking for answers. On the plus side he is a loving dog,my children adore him,recall fantastic ,ball mad and can sniff out his lost ball within seconds. I gave up my part time job as he became very distressed when left alone and i also needed to up his walks . He would spend all day outside if he could,i walk him 2-3 hours a day,morning and afternoon and that is not enough!! Unfortunately i did not research this breed before taking him on,he was too gorgeous to refuse but now i'm thinking 'what ever have i done' !