If it simply does not crank when hot, then the starter or its solonoid are bad - however, I would first double check ground straps and battery connections. If starter cranks, but does not start, then possible "vapor lock" caused by failed fuel pump check valve and/or leaking fuel pressure regulator that does not retain fuel pressure in fuel rail - and hot fuel vaporizes. Try turning ignition key from off to on 4 or 5 times (hear fuel pump cycle for about 1 second each time). Then try to start. Cycling the fuel pump refills the rail with cool fuel and purges the vapor.

Backfiring on deceleration - first check your throttle switch - clean the contacts and verify the setting (use test light on the idle contacts) Be sure that the idle has NOT been adjusted using the throttle stop screw - Idle can only be adjusted with the idle air needle valve - large screw below front edge of manifold (underneath the inlet pipe). Backfiring can also be the result of leaking injector and bad valves - check injectors for leakage/drippage and perform dry/wet compression test - and perhaps a leakdown test as well).

Hesitation/miss at highway speed. Several possible culprits - first, if you haven't already done so, convert your ignition from the points to an electronic system - there are systems that go inside the distributor and consist of sensor wheel on the disto cam, pickup and amplifier module that mounts where the points were, and two wires - a +12v lead to the pickup unit and a signal lead out that goes to the same terminal on the coil that the old points lead connected to. Next, clean the FI trigger contacts in the lower part of the disto housing - remove two small screws (being careful not to drop screws or washers - they are very short!). Disconnect plug and pull assy out the side - clean contacts with contact cleaner and a stiff card like a business card. (DO NOT SAND OR FILE!). Make sure rubbing blocks are lubed with distributor cam lube. Finally, in the throtle switch there are a number of contact strips and some contact bars. Carefully clean these and not whether any of the contact strips are badly worn - grooved or damaged. This usually occurs at the throttle position where you most commonly cruise - dirt or wear causes loss of contact and FI is momentarily interrupted - engine loses power and you naturally move acccelerator - contact is made again and engine runs fine - but repeats when you hit that spot again. Cleaning give diminishing returns and eventually replacement is called for.