Transimpedance amplifier with AD795, Guard Ring

I am building a transimpedance amplifier (TIA) to convert current into voltage. The current I'm working with is in the order of pico-amps, so my TIA has to be very precise. Below is a simplified schematic. D1 and D2 are for protection while Io is the voltage that the op-amp is biased to. This TIA is a replacement for another TIA module that has to meet certain requirements as shown on the left. My schematic, working with the AD795, is shown on the right. I've tried various simulations using LTspice, and it seems that the AD795 is the best choice for me. It has a very low input bias current, and it fits with my specifications.

Sorry, it's not shown, but I have two ceramic capacitors at each voltage supply node on the IC.

Looking at the datasheet for the AD795, I have questions about how to implement the guard protections. I think I managed to implement the guard ring properly below, but is it adequate? This is my first time designing a guard ring, so you can see how it looks like below. I started with a copper plane tied to Io. Then, I put a no-fill zone around my input node, and then I used vias and pads to 'draw' my guard ring. This way, no soldermask will cover up the exposed ring. The width of the guard ring is 20 mils (0.508 mm), except for when I routed under my two resistors. That is 10 mils. My diodes seemed big enough that I could route under them, and the addition of vias forms a via fence. I duplicated both my copper plane, the no-fill zone, and the ring on my bottom layer, so you see how it is duplicated. Is this correct for a guard ring?

One thing I was lost on was the other thing the datasheet said. Leakage through the bulk of the circuit board can still occur with the guarding schemes, so the datasheet recommends that the input pin be bent up and soldered directly to a Teflon insulated standoff. However, this seems more suited for a DIP package than an SOIC. How can I use this technique this along with the guard ring? Putting it on a Teflon post would still require the post to be connected to the PCB since the components are surface mounted.