S and Th are going to be problematic
The IPA describes every consonant the human head and throat is capable of making. Characters to the left of the below chart represent sounds made further forward in the mouth. Characters to the right are sounds made further back in the throat. Assuming that the rear portion of this creature's mouth are very close to a human's then the sounds on the right side of the chart should be pretty close.
Given the split tongue, this creature is going to have greater difficulty articulating sounds in the Fricative row as almost all those sounds involve some amount of air flow over the tongue. Since this creature's tongue isn't the same as a human's, we should expect a slightly different sound.
The presence of lips and nasal cavity means that Plosives and Nasal rows should still be pronoucable by this creature.
Also, read up on formants which talk about how vowels are formed. Holy crap, human speech is specialized!
Sure, if you've got the software to simulate this, great but just looking at the IPA chart and feeling around with your own head should be a pretty good start.