Your 2.75" shells, believe it or not, will hit harder than most 3" shells. They have more velocity, just have less shot. If your gun patterns well, you are not going to lose a turkey because of your ammo. As far as calls, a slate-type call is easy to work, and you'll sound like a turkey the first time you use it.
Calling frequency is a problem for a lot of hunters. You can call too much, but you can't hardly call too little. If you get an answer to your call, he heard you and he knows where you are. Shut up. You'll get a lot more action by playing hard to get than by seeming to be too eager.
There are exceptions, If you are working a gobbler with hens, it's a good strategy, to tick the hens off by trying to call the tom away from them. Everything they call you, you call them back. Tom's love two hens talking dirty to one another.