The bottom line is the CC is going to be squashed.
The first point to bring up is that in 3034 Thomas is not totally nuts and paranoid- there are tendancies, but they really grew and developed between 3028 (4th SW) through the death of his son Edward, the misjump into the Landmark system in 3047 and the Future Victor exercises of 3049. So in 3034/3035 he will still be seen as a reasonable and competent leader by his people. More then the betrayal he will be enraged that Grover went after his children- he places a high value on family (per Periphery 1e). And I wouldn't be so quick to say that the Pleiades Hussars support Grover- originally the TC trusted the CC only slightly less then the FS- they were both IS powers I think they only reason they did not fear them as much as the Davions was that the border with the CC was much smaller then that with the FS.
But getting back to why the CC will get squashed. In 3034 to 3035 the CC is still in the tail end of the war with the MOC and Andurien. After the pound they took in the 4th SW and the further damage in the Andurien War, they are going to be in rough shape- they probably won't have the forces to help defend MacLeod's Land- Grover would probably be on his own (looking at the CCAf roster in Brush Wars, in the 3030s, the CCAF is barely bigger then the TDF and probably in worse shape logistically). And unlike in the 3060s/70s, the TDF is not a technologically backwards force out matched on the battlefield, I suspect that they would do very well against the CCAF. So I figure when Grover throws his support in with the CC, Thomas (aided by Edward who by what little we know was actually in favor of contact with the FS much like Jeffrey) quickly takes back MacLeod's Land and gives aid to the MOC in their war against the CC. I can also see the TC driving into the CC, in the name of reclaiming lost Taurian worlds and well just plain retribution. (probably not going nuclear but hitting key bases and factories, etc). At this point I can see the FS and Candace Liao stepping in to "save" the people of the CC from their leader's stupidity. (Candace opposed a war to liberate the CC, but I can see her supporting efforts to save the CC from the depravations of the FWL, Andurien, MOC and TC). Overwhelmed on all sides, I figure the CC would collapse. Maybe a few worlds would remain loyal to Romano, but I could see many joining the St Ives Compact or remaining under the control of the MOC and TC.