If you really are doing CMOS analog design and you are using large resistors you're already heading in the wrong direction. There are all sorts of issues with resistors in CMOS processes like: parasitics (capacitance, non-linear capacitance), Low resistance values and extremely poor matching. NOC design (Non-overlapping clock) is trivial in comparison. At least you can be sure it will work in Si. I'd recommend a switched capacitor approach using differential signalling, there are even good topologies in layout that help cancel/balance stray capacitance effects.
Since you already have you floating capacitor (Feedback) you obviously are already using a MIM or PIP capacitor, you've all the modules necessary in your process.
As Andy mentions in a comment, you need a signal source that you can tune to make a frequency that you measure the filter with.
Luckily you say it is an Audio filter, so you can use an audio source.
Find a program that you can use in the freeware (or sample-ware) world to make signals around the cut-off frequency.
Use your scope to measure the signal going into the filter and going out. The scope can also probably even do some maths (since it's a digital one) and show "Input" - "Output" for you to easily then calculate the factor.
Since you designed the filter you should probably know about the log() scale of Decibels, but since I'm in a decent-ish mood today I'll continue to explain that the "cut-off" frequency is the 3dB point for many filter designs.
The 3dB point is where the power is reduced by a factor of two, but that means for the voltage that it should be a factor of sqrt(2) =~ 1.41 lower. Half the voltage output would be 6dB.
This website has a nice table to use if you don't feel like maths.
Many digital scopes can also (or have a purchasable upgrade for it) calculate the dB change in voltage. All you'd need to do is tweak the sine-wave output by the sound card until it says "-3dB". These digital toys have really taken the art out of it :-).
In fact, if it has "infinite persistence" you can make your soundcard sweep the frequency over 10seconds and then set the scope to a timebase that gets 10 seconds for a full screen and you can get a nice 2-line frequency plot and just use a ruler to instantly find a 3dB, 6dB or 20dB point.
Best Answer
try use some followers and cascodes to buffer the S, D & B of the output device. That way there'll be very little voltage across its gate oxide.
High VTH devices won't help (unless you're worried about subthreshold leakage) -- if you have any thick oxide devices, those might work better.