Technically, the Singapore air force has 7 squadrons of frontline fighters. Currently 3 are equipped with the F16. 3 more with the F5S/T. The last is converting to the F15.
In addition to the 7, there are 2 more squadrons based in the US (Luke and Cannon AFB) which operates another ~24 F16s (which may explain the discrepancy bet 62 and 94. There is a further training squadron in Cazaux, France.
In terms of basing, that's not a problem (due to the British investment in WW2). Airstrips exist at several locations including Tengah, Seletar, Paya Lebar and Changi. In fact, in the 70s and 80s, it used to temporarily house the RAAF Mirages as well. I believe existing bases can support further numbers if required. The USAF achieved greater concentration in Saudi Arabia during desert storm.
Airspace is tight but the numbers allow concentration in times of conflict.
IADS does appear to receive significant investment and regular exercises under the FPDA tests its effectiveness. The Singapore Air Force used to operate bloodhound SAMs (with 70km range). This was replaced by a battalion of I-hawk SAMs (which recently got upgraded with multiple engagement capabilities). Other SAMs used include Rapiers (which were also upgraded), Russian Iglas, Swedish RBS-70s and French Mistrals. That's a lot of SAM concentration for an island 40kms wide and 26 kms deep. There were reports that the military was looking into longer ranged sams as well (eg Patriots or SA-10s). This is also supplemented by the Fleet's Aster and Barak SAMs.
The navy has significant investments in maritime defence with FFGs and FACs that are equipped with Gabriel and long ranged Harpoon SSM. Hence, shore based SSMs do not appear to be needed. The fleet is also supplemented by Apaches with hellfires to deal with pesky small craft and harpoon-equipped Fokker F50s to deal with larger vessels. Since shore line is >40km wide, any craft equipped with harpoons will already be able to cover the entire coastline thus making shore based SSMs irrelevant. Worst case scenario, there's always shore based artillery.
Hope this answers the question....