This is a bit unclear even to me, but could 7 represent H acting as any other letter with a diacritical mark? As with Nohadon's name.
So the Palindrome could extend to 710 at the beginning with 210 at the end and the middle 7 could be replacing 52... or something.
So the numbers would be representing phonemes rather than letters, either individually or in combination. This implies that using letter substitutions would be unsuccessful, at least if we're trying to translate it as an English word as this language is phonetically irregular.
We'd need to match numbers up to these: http://www.phon.ucl.ac.uk/home/wells/phoneticsymbolsforenglish.htm if I'm right.