Whilst you're right that this is focused on Mises/Rothbard as Caplan acknowledges in his opening paragraph, it's fair to say that the economics of Mises/Rothbard is the strand of Austrianism that gets all the attention and funding; not many people describing themselves as Austrian economists are followers of Lachmann. So it's more akin to a criticism of Keynesianism which focuses on arguing most things Keynes, Hicks and the New Consensus macroeconomists said were wrong.

As for your points:

1. The position that ordinal and cardinal representations of utility are both valid in certain circumstances and in practice identical economic models can often be derived from them is the mainstream economics one which the Mises strand of Austrianism rejected. If you believe that "neither means the other is necessarily wrong" you're rejecting one of their core assumptions.

2. Indifference is pretty easily reflected in actions. Obvious example of a revealed preference of indifference between two items:
"Which one?"
"Either one"
(sure, I'll accept that in some cases a person might delegate a decision because they have a specific preference to give the delegate responsibility or to be surprised by the choice which is greater than their preference for one item over the other, but a lot of the time it's clearly genuine indifference between items. I'm not trying to impress the store clerk when I don't care which no-name manufacturer my $1 widget comes from). If Austrian economists insist on (re)defining economics as a set of immutable laws of human action, it helps not to have such obvious counterexamples to one of their claims...

3. Austrian Economists following the approach of Mises insist that modelling dimensions as continuous functions is never acceptable. ergo if you believe continuous dimensions are sometimes a useful modelling assumption, that's a pretty good reason not to be an Austrian economist (even if you think their objections to the representation of some dimensions as continuous differentiable functions are valid; it's not like Austrian economists are the only people offering such critiques)

4. Considering that the thrust of Mises/Rothbard's arguments is that government is [almost always] bad for allocation of resources, it's a pretty major shortcoming that based on their own foundational assumptions they can't actually argue that even the most egregious examples of government misallocation of resources actually are misallocation of resources.[1] (Many mainstream economists also argue against the validity of interpersonal comparisons of utility, but could at least have some grounds for argument that lesser quantities of output under a price-fixing regime are suboptimal on the grounds of Kaldor/Hicks inefficiency since they're willing to consider non-revealed preferences.)

5. Caplan doesn't elaborate on this particularly well, but it's a standard claim by Austrian economists that mainstream approaches involving quantitative analysis aren't compatible with the concept that value is subjective. It's also pretty well established that many classes of quantitative mainstream model work pretty well with Austrian-style subjective preferences (viz. based on ordinal preferences within a budget constraint).

[1]obviously Austrians have lodged other objections like claiming that allocation of resources for production in the absence of a price system is "impossible" (clearly incorrect) rather than merely less efficient, and generally subscribe to ethical arguments that government intervention is "coercive" except when used to prevent people from using resources other people claim ownership over. But not being able to say "West Germany produced better economic outcomes for its citizens than East Germany, or even than medieval Prussia" is a pretty major disadvantage in an economic theory.