I would seriously try the hevi shot!
I use the Hevi shot magnum blend,it has #5,#6  shot in a shell.
But regular #6 hevi shot is great also.It has the knockdown power of regular #4 turkey loads.
PLUS,u get more pellets in the shell using hevi shot without sacrificing knockdown power!Which is perfect for smaller gauge shotguns.
Its exspensive,But after all ur hard work,wakeing up early every morning etc.
And when u finally get that turkey to come in,It is all worth it!
As for calls,I prefer the woods haven mouth calls.
Any friction call,that u can get a decent yelp out of will work,
Slate calls are among the favorite.
If ur having trouble with using those calls,
Buy one of the push button yelpers.My son takes birds every yr with one.
Good luck & have fun...