First in our current system the president needs Congress to get things done
There is quite a lot that the President can do independently using Executive Orders. Even tasks that, on paper, require congressional approval can be subverted, and you can look at the US's record of entering undeclared wars as evidence of that.
Beyond that, see what I already said about how there's no such thing as an autocrat.
Second, we’ve seen with the freedom caucus that a small group of congressmen can wield a lot of power
These are people who would do the best in an imaginary Fuhrer Trump political machine. Think of it like getting promoted to a bigger, more powerful Freedom Caucus.
Third, I think we definitely can expect a very different Trump in a second term versus his first term and he definitely HAS expressed an interest in this with all of his dictation envy too become Fuhrer and worse there is a large portion of the population that is content to be rolled under a Trump dictatorship.
People have been talking about him admiring dictators before he was elected and all throughout his first term. There's nothing new here, no evidence that suggests something has changed.
I promise you it's just hysteria. So there's a chance of something beneficial happening in this conversation, I want you to just take note of this conviction you have that Trump will be Hitler and then, if he is elected, just remember it as he blunders his way through being racist and doing war crimes just the same as he did before with no particular change besides Vance leading a new rhetorical tact.
No, I won't be doing a mirror version of this exercise. I'm a communist, so if I'm wrong and he's a neo-neo-Nazi, I get the wall anyway and it's no harm done.
Some things aren't compatible, and trying to combine them results in having one with the skin of the other. Liberal democracy, for instance, is incompatible with monarchy, and we can see in the UK for instance how the liberals kept on gaining ground until the monarchy became totally symbolic (a very expensive symbol, but a symbol nonetheless). If the workers having democratic control of the means of production precludes capitalists having plutocratic control, it's very simple. Put in the same environment, these two forces would bear what Marxists call "class antagonisms" towards each other and struggle until one was subordinated to the other.
The US (we'll use that example because I know it the best) does borrow ideas from various economic theories, those being various sects of classical liberalism, Keynesianism, and the odd bit of Austrian School or Christo-fascist policy. That is to say, different sects of capitalist ideology. You do not see policies based on Marxian economics or anything of the sort, it's just empirically not how US policy gets written, and that shouldn't surprise you.