At first, you should co-register your images using back-geocoding functionality, that supports Sentinel stack co-registration now. (Radar -> Coregistration -> S1 TOPS Coregistration -> S-1 Back Geocoding)
Secondly, SNAP didn't allow me to export with "topo-phase removal" step done. So I didn't do it by now.
Mine processing chain looks like this:
Apply Orbit File to each image -> S1 tops split -> back geocoding of stack -> interferogram formation -> Add elevation band to last product in the chain
Talking about deburst and subset operations I am not fully sure yet. It seems that you can deburst, subset co-registered stack and interferogram stack individually or deburst, subset at first and then generate interferograms out of subset.
Don't exprort too small area. It should be definately larger than 2km x 2km. Otherwise StaMPS will find zero permanent scatterers.
During step nr. 6 you may need to decrease values of parameters "unwrap_grid_size" or "unwrap_gold_n_win". The less image you exort, the more parameters will need to be decreased.
I still have some problems incide StaMPS though. The image is stretched, points are geocoded near zero co-ordinates and deformation values are unnaturelly huge.