As Electron said earlier, you can also get decent RG-6 cable and a balun at Home Depot and Lowe's. If you see a balun that was made in Japan, buy it (avoid gold plating)! Otherwise, no one balun stands out over another.
Your antenna is just fine for picking up Boston and Providence. It has a modestly wide range of azimuths where it is modestly to very sensitive to signals, so your aim does not have to be laser accurate for Boston. Since you have a VHF section, why not try to use it? I would start by aiming almost due south by a compass to get WNAC and WPRI. If you can get those plus all the stations in the green part of your report, then you're done. If you don't get them all, start stepping counter-clockwise 5 degrees or so until you get everything you want.
Good luck!
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