No, I would not suggest using the tooling board at 142°C. The 130°C is the maximum service temperature and so that should not be exceeded. What happens past 130°C is that you're into the Tg (glass transition) of the epoxy resin used in the board. Being into the glass transition temperature and then putting positive autoclave pressure onto the board will effectively 'push' the laminate into the surface of the softened board, almost certainly causing the laminate to print onto the board, affecting the surface finish and quite possibly causing it to stick.

Furthermore, one thing you might not have considered is the coefficient of thermal expansion (CTE) of the board. Although the board has a Tg of a little above 130°C, you should also consider the CTE of the board when using it at the higher end of its service temperature. Even at 100°C you will get noticeable expansion from any epoxy tooling board, including our EB700. This means that its dimensions will be measurably different at 100°C and they will be even more different at 130°C. If the prepregs you're talking about are carbon fibre prepregs then these have almost zero CTE and so - depending on the geometry of your pattern/mould - you could find yourself with the component being either mechanically locked into the mould or rattling around in/on it, when the board cools.

Most often, even for low volume production, epoxy tooling board is used for a long low initial cure, followed by a demould and then a steady-ramped post-cure freestanding.

As for sealing the board, yes, you absolutely must do this, even for one part. If you don't want to invest in a dedicated board sealer then it is possible to 'seal it' using enough coats of release agent. but you will need to build up a LOT of coats because tooling board can be quite thirsty and absorb a lot of the early applications deep into the board.