Folks, it isn't as dire as you might think: you WILL be able to get all your significant local Seattle-Tacoma stations if you use the right antenna system. I believe that you own, and are referring to the ClearStream2 antenna made and sold by AntennasDirect. It is an antenna intended for close-in reception of UHF TV stations. That antenna will NOT solve your current TV reception issues, as you need a fringe-area antenna that will receive VHF as well as UHF antenna to see all of the Sea-Tac stations well.
The major Seattle stations come from two different directions from your location: the bulk of them transmit from a location near downtown Seattle, however KCPQ, the FOX station, transmits from a location about 25 miles WEST of downtown Seattle. Your home has a clearer shot to the KCPQ transmitter, so I suspect that you may be more easily likely to see it's signal than KING, KIRO, KCTS, KOMO, KSTW etc..
I have solved this issue a number of times for other Washington residents, and I believe that I have the answer for you, as well. You need a two-antenna arrangement: a broadband VHF-UHF antenna aimed at the bulk of the Seattle transmitters, which are located 340 degrees from your location, as measured by your compass. I would recommend using a Winegard HD-7696P antenna mounted on the highest point of the roof of your house. You will need a separate VHF antenna to pick up KCPQ . I recommend using a Winegard YA-6713 or an AntennasCraft Y-5-7-13 mounted 4' above the larger broadband antenna , and aimed at at 305 degrees by your compass. Combine the two antennas using a Channel Master JoinTenna tuned specifically for channel 13, which is available cheaply from Amazon.com. Feed the output of the JoinTenna into a Winegard HDP-269 preamplifier, and mount the power injector for the preamplifier in a location inside your house that is convenient to both your primary TV set and your mother-in-law's TV set. Mount a high-quality 2-way splitter inline after preamplifier's power injector, then run cable from the splitter to each TV set. Be sure that you rescan the digital convertors after the installation to be sure that they find the new channels. All of your local network channels should be restored, and you should receive signal equal to or better than the satellite or cable TV signals in your area.
http://www.winegard.com
http://www.antennaCraft.net
http://www.solidsignal.com
http://manuals.solidsignal.com/AntInstallGuide.pdf