I have a 1999 Dodge Neon with a 2

How did you check the compression if it doesn't crank? Are we talking about a starting problem or a no-start condition? 100 psi is rather low and would point to the timing belt off a couple of teeth. Have you checked the fault codes? Which engine do you have, single or dual cam?

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I can think of two things to check. First of all, I know you said you have good spark but that fooled me on one. If at any point you disconnected the battery or ran it dead, any stored fault codes would have been erased, and may not set again right away. In particular, the code would be "cam and crank sync". At one tooth off on the timing belt the Engine Computer will turn on the Check Engine light and set that code. At two teeth off it will shut the engine down to protect the valves. You may still have spark from one of the two coils. That's what fooled me. That spark was sporadic, ... And the injectors were not firing consistently. That's because the computer wasn't keeping the automatic shutdown (ASD) relay turned on steady. At three or more teeth off the open valves will hit the pistons as they coast to a stop.

The common problem is not that the timing belt has jumped a tooth. The camshaft timing is late because the sprocket has turned on the camshaft. The camshaft position sensor doesn't look at a point on the sprocket. It looks at a point on the driver's side end of the camshaft. Tie the timing belt to the sprocket, then remove the sprocket and check if the dowel pin is sheared off.

The other thing we've run into, twice on the same day, is bad gas. After wasting almost a whole day on the first one, the mechanic drew out some gas, dumped it on the floor, and threw a lit match on it. It put the flame out! Draining and refilling the tank solved the no-start.