Are these acrylics suitable as a paint for pouring?

Yes, but you will get through certain colors very quickly therefore the jumbo tubes may be preferable. Try mixing with PVA (polyvinyl acetate) and water.

Can these paints be used for fabric painting e.g. canvas shoes? And for outdoor items like plant pots, signs?

Yes, they can be used on canvas shoes but you should seal with a clear waterproofing agent. Regarding outdoor items, allow to fully dry before exposure to rain. A coat of clear varnish will offer protection.

Can I use these on glass?

Yes, as long as the glass isn’t going to be washed and you are very careful. Why not try clear perspex as an alternative.

Are these suitable for using to block in colors in order to then use oil paints over them?

They are a superb ‘fast drying’ option for underpainting oil paintings.

Can Castle Arts acrylic paints be used to paint on wood?

You can - use the paint straight from the tube and minimise the amount of dilution to stop the wood from warping. Try first coating the surface first with a proprietary brand white primer.