The short answer is, no, this is not accurate.

It's been a long time since I've read his books and I don't have them with me, so I can't do a detailed takedown, but Grossman's books are problematic. While many of his assertions about the nature of combat are fundamentally correct and do explain various phenomena observed across military history, the methodology he uses is unscholarly and I would be hesitant to trust any given statistic he cites.

Now, to your question. There's two components here - range and casualty rate - and I'll address them separately, starting with range. 30 yards is far too close. British historian Paddy Griffith once gave an average range for Civil War firefights as 141 yards, which is far more reasonable. Contemporary accounts of battles contain numerous examples of firefights in the several hundred yard range. The mechanical accuracy of a Civil War rifled musket - that is, how accurate the weapon is physically capable of being, ignoring the limitations of the operator - is more than sufficient to hit targets at these ranges and beyond. And if you've ever walked a Civil War battlefield, you'll find that 100 - 200 yards is a common range to find opposing lines. Of course, not all muskets in the Civil War were rifled, especially not during the first two years. But even then, based on accounts from the Napoleonic Wars, around 100 yards is a likely range for a firefight with smoothbores. This is not to say that firefights never took place that close; there's numerous variables involved, with terrain playing a huge factor. But as a general rule, if two opposing lines were much closer than 100 yards, one side was charging the other. Sometimes during a charge, units would stop to shoot and reload, and it's completely possible for volleys to have been exchanged at 30 yards during a charge, but it's a preposterously short range to propose as an average.

Regarding the claim of 1-2 soldiers killed per minute, that is plausible, but not without explanation. First, what size regiments are we talking about? Civil War regiments were generally raised with around a thousand men, but they were rarely at full strength due to disease and casualties, often dwindling down to just a few hundred or even fewer. Obviously, all else being equal, 400 men shooting at each other will cause fewer casualties in a minute than 2000. Second, we should distinguish between "deaths" and "casualties." These two terms are often thrown around interchangeably, but especially in military terms, they have distinct definitions. Deaths are self-explanatory, but "casualty" is a broader category that includes deaths, but also includes other personnel rendered unavailable for combat. The most common breakdown is killed, wounded, captured, and missing. So it is quite possible for two average-sized regiments to be shooting at each other and for only 1 or two men to be outright killed per minute, but it's almost guaranteed that in addition to those deaths, more men will be wounded. Numbers can vary wildly between battles, but a good rule of thumb is about 5 men wounded for every 1 killed. Third, there's an implicit assumption that there's a linear relationship between the number of casualties inflicted and the length of a battle, and this is a bad assumption. Casualties would often be higher earlier on in a firefight for two reasons: first, officers could only keep good control of the men for so long. For the first few minutes, they had better control over firing coordinated volleys, exhorting men to "aim low," and otherwise influence their troops to be more effective. The longer the firefight continues, the more this control breaks down, reducing effectiveness. The second reason is black powder smoke. Unless it was a particularly windy day, after a few volleys, a battlefield could be so clouded with smoke that soldiers couldn't easily see their enemies, making it harder to shoot them, thus reducing casualties inflicted per minute. It's entirely possible for a few initial volleys to have killed dozens of men, followed by more minutes of mostly ineffectual shooting that, when averaged out, comes to 1-2 men killed per minute. But that one statistic, while accurate, wouldn't be descriptive of what had actually happened.