Into March 43 there were only two Italian infantry divisions of variable strength, some corps units, and militia. I'm unsure about coast artillery. Air strength was at a low of 130 operational aircraft in November, which increased after 6th Nov. It appears the airfields there were capable of supporting more than 130 on a permanent basis, but its not clear if the Axis were doing more than staging raids off the air fields & keeping the aircraft out of reach. The P-40 could escort to the south end of Sardinia & Allied bombers attacked the airfields there with increasing frequency. They were considering the PEDESTAL operation, just 87 days earlier. The oil slicks from the dozen odd Allied ships sunk were still there when Op TORCH planning was underway.
Landing at Bone puts the amphib fleet in range of the Sicilian airfields. While Sardinia had a relatively weak air strength Sicily was scary. Of the 650+ sorties flown against the PEDESTAL convoy better than 70% were from Sicilly. Conversely the Allies were a bit better prepared to deal with submarines in November. Those accounted for much of the damage in August & had there been only damage/sinkings from aircraft the PEDESTAL operation would have been considered much more successful. Also the Italian surface fleet was less a threat/distraction in November. Unlike in August the Axis were caught by surprise & the Italian fleet less ready to sortie. Landing at Bone, or further east is one of those operations that looks really risky, but has not just operational but big strategic payoffs if it succeeds.
As far as the Sardinia and Corsica garrisons go, English language sources on-line are mixed, but from what I can tell, in the summer of 1943, it stacked up as follows:
German: 90th PGD (Sardinia); SS RF PG Brigade (Corsica);
Italian: 20th Infantry (Corsica); 30th Infantry (Sardinia); 31st Infantry (Sardinia); 44th Infantry (Corsica); 47th Infantry (Sardinia); 184th Parachute (-) (Sardinia); 203rd CD (Sardinia); 204th CD (Sardinia); 205th CD (Sardinia); 225th CD (Corsica); 226th CD (Corsica);
That's a German motorized division, four Italian infantry divisions, and three Italian coastal divisions in Sardinia, and a German motorized brigade, two Italian infantry divisions, and two Italian coastal divisions in Corsica. Obviously, a German or Italian division was not directly comparable to a US Army or British Army division in 1943, but the Axis forces in Corsica were (roughly) equivalent to four reinforced Allied divisions and those in Corsica were (roughly) equivalent to two reinforced Allied divisions. So call it two corps equivalents between the two islands, both significantly smaller than Sicily, which would suggest an Allied expeditionary force that would have to be roughly an army in size - so about half to two-thirds of the HUSKY assault force?
Good point re the realities of PEDESTAL. Mounting an effective amphibious operation east of Algiers would require a lot more assault troops, amphibious and follow-on shipping, naval escort and covering forces, and more carrier air power. In the autumn of 1942, the only theaters where the Allies could have found those forces would have been the South Pacific and Indian oceans ... which seems unlikely.