1. You can mount a dial test indicator on a small magnetic base and stick it to the cross slide. That will be fine to align work in the chuck. Another method would be to mount the dial test indicator in the tail stock chuck.
2. You can attache a 16 gauge piece of sheet metal to the maple block. It works quite well for holding the magnetic based indicator.
sometimes fit mine to a bit of bar held in the toolpost. A bit of bent bar may be more versatile allowing the DTI to be mounted at different andles. Otherwise you can fit it to an old scribing block and just stand it on the wooden base the lathe is on. It helps if the base is made from something like a bit of kitchen worktop, with a smooth flat surface. Scribing blocks usually have an adjusting screw which allows fine setting.
In general the Unimat is too small to easily mount the larger DTIs. Using the surrounding surfaces makes it much easier.