Why are FFT numbers so high?
As pointed out by Dan Boschen in a comment, these number aren't really surprising. Usually the DFT is defined as

$$X[k]=\sum_{n=0}^{N-1}x[n]e^{-j2\pi kn/N}\tag{1}$$

where $x[n]$ is the input sequence and $N$ is the DFT length. So bin zero, i.e., $X[0]$, is just the average value of your input sequence multiplied by the DFT length. The maximum value of $|X[k]|$ can be as large as the maximum value of $|x[n]|$ multiplied by the DFT length.