I'd get the CM 4228 if I were you.
- It's one of the highest gain antennas you can buy.
- It's not as directional as a yagi-style antenna, so it'll pickup your 6 degree spread better than a yagi
- Its design makes it very attic freindly... Just ry aiming a yagi in a stud-dense attic and you'l see what I mean
- Although it's a UHF antenna, it can pickup some VHF, especially the higher channels... Only your PBS channel is PBS on ch 9, so you may be OK with just a 4228
- It is an easy antenna to "stack" if you need more than one to increase signal strength
- Lowes carries CM products, so you should be able to get one locally
- If Lowes does not have it, Warren Electronics has them for a great price (though the shipping may be in the $teens) In the end, though, Lowes price + tax will probably be about the same as warren + shipping.
I recommend using a CM7777 preamp as well. It's a great amp, and may actually be too much for how close you are to the towers (we'll address that in a moment), but it will ensure yuo get a strong, low-noise signal from your antenna to your receiver. You can get one of these from Warren as well, I think Lowes only sells CM's cheaper amp models, but it wont hurt to check.
Now, here's something else to try... Go to radio shack and but a variable (0-20db) attenuator. Buy this before you buy anything else. There's a small changce you're overloading your receiver and getting "false" low signal strength reading. If I directly connect my amp'd antenna array to my receiver, I get sub-80's all around. If I connect the attenuator between the amp and receiver, and dial in about 8db of attenuation, I get 97-100% on nearly all my channels. This even increased the reception of my own PBs VHF station from a shaky mid-60's to a stable 80's. An attenuator may solve your problems with your current antenna, and will probably come in handy in your future endevours.
Finally, the other good thing about a CM7777 preamp is that you can use it in a combined input or seperate UHF/VHF input mode. The nice thing about this is you can have seperate UHF and VHF antenna if you want (configurable by a switch inside the amp, as is the FM trap). So, you could first try the 4228 has a combo antenna, connected to the unified input, and later, if you have trouble with PBS, hook up some rabbit ears. lke Rick suggested (with a balun/matching transformer) to the VHF input to get channel 9. You could adjust the length of the rabbit ears to perfectly match the wavelength of channel 9 (There's a website somewhere with these figure, I'll have to post it) since it's the only VHF you need.