My main issue with Sardinia is that Kent Hewlitt and Mary Cunningham specifically rejected any invasion outside land based fighter cover during this period. and I think they know more about the matter than you or me.
The actual numbers of a/c available TTL are speculative - how many lost in Libya for example.
OTL there were 80-100 a/c in Sardinia more or less permanently with between 50 and 75 bombers. With a further 500 fighter and 300 bomber in Italy/Sicily with up to 100 FB and DB (most were in Libya OTL) and Luftflotte 2 say 220 a/c all types. KG26 was at some point based there. as were a lot of the Italian anti shipping units.
Stolen from Axis History Forum the airbases are:
SARDINIA
Permanent Airports/Airbases:
Cagliari-Elmas - Most important airbase with fixed installations with at least an hard surface runway in 1940, operative also by floatplanes.
Monserrato[ - Airbase with fixed installations employed apparently only by fighters.
Alghero-Fertilia- Airbase with fixed installations, bomber level, hard surface runway at least in 1943. The rare bombings of Gibraltar made by S.82 was done from this airbase, which means it had a runway long enough for overweight S.82.
Olbia - Airbase but with scarse support- operative by floatplanes too.
Campo di Manovra- Maneuver landing grounds that went operative at war start or during war:
Villacidro (Trunconi)(nº9)- bomber Stormo(36 bombers) at start, can be big. Me 323 operated from there later.
http://www.villacidro.net/zzz/storia/1939-40.htm
Decimomannu(nº39) - bomber Stormo(36 bombers) at start, can be big.
Milis - unclear if it existed at start, bombers operated from it 1942 at least.
Case Zeppara(Sa Zeppara) - 1200m compacted earth surface runway build already in war, some building was done including hangar but only for supplies and ammunition, the air personnel was dispersed around the camp . Operated by torpedo bombers.
Santa Giusta - Idroscalo(flotplane base), some sources say it was abandoned during war because of malaria.
Oristano - Bomber able, some say it had a hard surface runway in 1943. Some references to Malaria also.
Chilivani- being prepared at war start(10 June 1940). No more data.
Venafiorita - bomber able at war start, operated Me 323 later in war.
Campo di Fortuna- small emergency landing grounds - most if not all build during war:
Milis E.17a - alternative landing 3km south of Milis - build in war.
Borore
Villacidro-Forru
Villacidro-Cotta x2
There were more emergency landing grounds but i don't have info on them. Any big landing ground should have at least one diversion emergency landing ground nearby. Villacidro for example had 3.
Others:
Ottana - operative in 1943, unclear if earlier. Unclear if Campo di Manovra or Fortuna.
Capoterra - no data.
CORSICA
Airports:
Bastia
Ajaccio(Campo dell Oro) and Aspretto Floatplane and Naval Base.
Landing Grounds:
Bonifacio
Porto Vecchio
Ghisonaccia
Travo
Borgo
Calvi
Ajaccio(Valinco Gulf) - emergency
The corsican airbases alone could handle 480 A/C according to an invasion study. And Decimomannu is by 42 a major base - still is in fact. you will have to look up where they are but there is a resonable scattering across the island.