I have been Baal Tshuva for almost 20 year, almost half my life. I have been working on my Kavannah for a few years now, and feel significant improvement in some areas like Brachot and the Amida. I generally Daven in a Minyan 2 or 3 times a day. My problem is maintaining concentration during the longer Davenning services. I’m fine for Mincha and Maariv but some mornings, especially those with Mussaf and/or Torah readings (soon Slichot!) I get restless, loose focus, feel hungry, and generally find it hard to concentrate for most of the time. There is a bit of a paradox, because I feel there is never enough time for the silent amida, but so much time devoted to other things. I have small kids at home and often feel I should rather go home early and help my wife with them. Any advice?

You should not go home and and help your wife. Help your wife before Shul, after Shul etc. but not instead of Shul. Find a "no-frills" Minyan without "Mi Shebeyrachs" that will not tax your concentration. In some places there is an "early" or "late" minyan that on Shabbat takes an hour and a half or even less. If you get hungry during Davening, it might mean that you should eat more before you leave for shul.