Just because bubbling has stopped doesn't mean fermentation has completely stopped.
OTOH, Wyeast says alcohol tolerance for 1968 is 9% and the ABV calculators put your stout at around 9.5%. So, it may well be as far along as that yeast can take it even though attenuation % for that yeast implies FG should go a bit lower.
Assuming 1968 has done all it can due to alcohol content I'd think warming it isn't going to bring about any appreciable change in FG. Not sure what you'd do now other than bottle/condition or maybe pitch something with higher alcohol tolerance if you want lower FG but not too sure that's very good advice.