Question: I got excited about Calc's power as an embedded mode. Define some variables in natural inline notation and then do operations on them. 

But the execution seems a bit messy: you got a separate key bindings when you're in CalcEmbed mode and mistakes are easy to make.

Can the mode be tamed so that the following org-mode buffer:

```
* Calc test embed!

Let $foo := 342$ and $bar := 2.2$. Now $foo*bar => $!

```

Could be evaluated to 

```
* Calc test embed!

Let $foo := 342$ and $bar := 2.2$. Now $foo*bar => 752.4$!

```

With a single key stroke, all the while remaining in org-mode?

Answer: 
Maybe not a single keystroke but you could *activate* embedded mode via `C-x * a` and then (while point is in, say, the first expression) *update* all calc expressions with `C-x * u`. I use embedded mode all the time and it's one of the most understated features of Emacs!
To expand on @éric's answer: you can avoid having to activate the formulas explicitly with `C-x * a` by including these lines:

```
--- Local Variables: ---
--- eval:(calc-embedded-activate) ---
--- End: ---

```

In an org-mode file, using just `#` instead of `---` is probably better though. Also notice that this and `C-x * a` doesn't actually *activate* embedded mode, but just activates the formulas for embedded mode, so you stay in org-mode. (See [doc for `calc-embedded-activate`](https://www.gnu.org/software/emacs/manual/html_node/calc/Assignments-in-Embedded-Mode.html#index-C_002dx-_002a-a) for reference.)

Also, you can call `C-x * u` with a numeric prefix, which will update all activated `=>` formulas, so you don't need to move the point into a formula first (e.g. `C-- C-x * u` but not `C-u C-x * u` which will only update formulas in the current region). In itself, `C-x * u` will only update formulas which are dependent on the current formula (i.e. where the point is pointing at). (See [doc for `calc-embedded-update-formula`](https://www.gnu.org/software/emacs/manual/html_node/calc/Assignments-in-Embedded-Mode.html#index-calc_002dembedded_002dupdate_002dformula) for reference.)