When I read in public I read exactly as it is written. I invent no "qamats qatan", no "schwa mobile" and no "dagesh forte", and it comes all out very good.Do you, claiming that you don't read qamats qatan as [o], read ישמר differently in יִשְׁמֹר and יִשְׁמָר־ (whether joined by maqaf to the following letter or bearing a pronominal suffix)? In other words, do you read the ḥolam in the red below differently than you read the qamats in the blue?
יְֽהוָ֗ה יִשְׁמָרְךָ֥ מִכָּל־רָ֑ע יִ֝שְׁמֹ֗ר אֶת־נַפְשֶֽׁךָ׃
יְֽהוָ֗ה יִשְׁמָר־צֵֽאתְךָ֥ וּבוֹאֶ֑ךָ מֵֽ֝עַתָּ֗ה וְעַד־עוֹלָֽם׃
Nearly everyone who reads this pronounces both as the same imperfect form: yishmor. It doesn't matter if it's independent (יִשְׁמֹר yišmōr) or joined (יִשְׁמָרְךָ yišmorḵá or יִשְׁמָר־צֵאתְךָ yišmor-ṣēʾṯḵá).
The only question is how to read the hatephim which are made up of a double marking.
Isaac Fried, Boston University
www.hebrewetymology.com