I don't know the particular mic you are using, I've done a wee google on it, and can only really offer you the following advice:
1. Although you mention the impedence, you don't mention the actual output -usually displayed as V or mV, although it's internally powered (via AA) the actual output of these mics can vary massively. The term 'microphone level' is often used, but this is really a cap rather than something that every mic will output. For example, I have a sennheiser K6/ME66 which runs from an AA and is lovely and strong, I also have a couple of Sony ECM-77 tieclips which run off AA's and are too weak to use with a DSLR, unless in phantom mode, via a powered pre-amp. A solution that I don't think is suitable for your mic.
2. Is this an accoustic gig, or is there a PA?
If there is a PA then your options are to take an XLR line from the mixing desk into your tascam, getting a nice clean feed from the mics already on stage, or placing your sony mic next to one of the monitors, which should give you a much better level. Obviously gaffer taping down cables etc. If it's an accoustic gig then you want to get your mic as close as you possibly can to the source, the closer you are the clearer and louder the audio. Again you could run it into your tascam which could be at the base of your mic stand, although this will cause monitoring problems.
3. Camera connectivity and controls.
You need to set the cameras record levels up manually. Use the VU meters and have the audio peak at around -12db. You really want to achieve this with the mic level no more than 1/4 from the left. Any more than this and hiss will be intrusive.
Unless you have an XLR adaptor such as a beachtek or juiced link on your camera I would be tempted to use your tascam and monitor off that (this would mean a cable run between the mic position and the camera / tascam position, so again health and safety, tape everything down)
4. General rules for micing:
-Get your mic as close to source as you can without being in shot. This gives you the best level and best perspective.
-Camera top mics are fine for ambient wild tracks. It is the worst postion for a mic as it will pick up your handling noise, your aperture noise, your breathing, any other animal person or object in between the camera and the subject.
-Sound is more difficult to get right than video, and usually mistakes are more towards the fatal end.
-On DSLR audio is pernickity. A lot of folk use external recorders for good reason. I certainly wouldn't adapt an XLR balanced mic to minijack straight into the camera. Lots to go wrong.
Can you explain a little more about the scenario, specifically:
Is it being mic'd by a sound engineer to go through a PA (let them do the work, tap a recording)?
How close can you get with the mic?
Can you get the XLR from the mic into the XLR port of the Tascam?
Can you synch the audio from the Tascam with the video and guide audio from the 5D at the edit stage?