Difficulty in using tamil fonts for sanskrit texts

I have macbook pro, iPad (from the oldest to the latest) and iPhone 4. I use "tamil 99" fonts (built-in in all). At present I am converting some of the sanskrit sloaks into Tamil.

When doing so, there are occasions I need to draw a single line (mark), double lines and at some places line (similar to under score) below the text.

Presently in the fonts there is provision to make a dot only.

Also I tried in the sanskrit, the results are the same.

What I am doing at present is type the text, print and physically mark, scan and send it to the required.

Herewith attaching a sample text for reference.