ronsimpson:
Yes, 5% should suffice, but the distributor I'm getting my components from sell 0.1% resistors for a cent extra each. Doesn't hurt to buy them =)
I've placed the order, now to wait for them to arrive.
MrAl:
Yes, I should be driving at constant power but the diode I'm using (OPV300) does not have a built-in photodiode. The diode does have pretty tight specifications, so hopefully, by keeping a safe margin and some voltage clamps on the op-amp side, things won't go wrong.
Regarding the op-amp, I have switched to using a dual supply.