Can we compare the slope for specific value for a fixed effect in GLMM

Question

I have the following model:

model <- glmer(resp ~ predictor1 * predictor2 + (1 | subject),
               data = df,
               family = binomial(link = "logit"))

My variable 'resp' is binomial, 'predictor1' and 'predictor2' are continuous. I'm interested in comparing several values in predictor1 but for the example I'll stick with 2 values: -12 and 0.

Using the bootMer() and predict( ) functions, I modelled the data to produce this graph:

I did find a significant difference in my fixed effect 'predictor1'. I illustrate this with the following graph, extracting the probability at 50%::

My problem is that I'd like to do the same comparison (and graph) for variability (i.e. the interaction of fixed effects). I was thinking of doing the point difference at 75% and 25% but I wouldn't have the confidence interval, unless I'm wrong?