Need help to increase schmitt trigger sensivity in a circuit
Your main restriction to getting better performance is the ADA4075 and its power rails. The data sheet suggests it can't be used on power rails below +/-4.5 volts and you have it on +5 volts and ground i.e. you are not powering the thing correctly. May I suggest that if all you have is a 5 volt rail, you use a 5 volt rail-to-rail device.

Even if the power requirements are met, you also have a further issue and that is the common-mode input voltage range. For the ADA4075 it is specified as +/-12.5 volts when powered at +/-15 volts and this means that you cannot rely on signals that are within 2.5 volts of the power rails you apply. Given that you only have a 5 volt rail this is a serious nail in the coffin for using this op-amp.

And a further nail is the output voltage range. This is specified as typically +13 volts and -14 volts (on a +/-15 volt rail) so there are potential problems here too.

May I also suggest that after you change the op-amp you get rid of the Schmitt trigger and use the "proper" op-amp as a comparator with variable threshold level and variable hysteresis.