Distinctioning ''pan'' and ''pen'', and ''home'' and ''hum''

I'm a Non native English speaker and I'm having a hard time distinctioning ''pan'' and ''pen'' (both of them sound like ''pen'' to natives when I say them) and also ''home'' and ''hum'' (both of them sound like ''hum'' to natives when I say them).

How do I make the distinction between the vowels in ''pan'' and ''pen'' and the vowels in ''home'' and ''hum''?

I'm also having a difficult time distinctioning ''pull'' and ''pool'' (both sound like ''pull'' to Natives when I say them).

What's your first language?

My jaw is much lower, and mouth more open, for "pan" and "home". My jaw is nearly closed for "pen" and "hum". Try just dropping your jaw for the first two.

Also, the word is "distinguishing", not "distinctioning".