Would almost be a suffix for without?

Answer 1

No.

A suffix is a two or three letters added to a word such as un- added to comfortable makes the word uncomfortable.

If you add almost to without you have almostwithout which is not a word you will find in a dictionary

Answer 2

The suffix "less" can be used to convey the meaning of "almost without" or "lacking." For example, "careless" means almost without care, and "noiseless" means almost without noise.