A Ford Model A wheel with a crack or two has never been a problem for a million wheels that have been driven with cracks for over sixty years. These wheels are just about indestructible.
Spend some time researching the design, materials, building and manufacturing of these wheels - and the Ford (and later, non-Ford) literature on the Model A wheel, and you will find that this wheel will not fail with any number of flaws and 'issues'. They are pretty much 'bullet proof'.
Of course there are a number of issues that you should be concerned about in a Model A wheel. But a crack or two is not one of them, from a safety standpoint. I can already hear the howls of protest to this statement, but I stand by it, based on my own and others, 65 years of driving experience.