My Vowels: Heed, Hid, Head, Had, Hodd, Hawed, Hood, Who'd

This was a very interesting exercise for me as it made more real all the very theoretical stuff that was in the reading. I have a hard time figuring out what it means that a vowel is closed, or open, or back in the mouth, or in the front. The "whispering" and "creaky voice" techniques worked to some extent to help me figure that out, but more important was making my own vowel chart.
I had some trouble with Praat and figuring out with frequencies to use (where in the striation band), but I generally picked an area in the middle and I hope that was accurate. It may not have been though, as seen in my results. I was wondering what the blue line that shows up in Praat is, with blue dots connected... it seemed like the upper border of my first formant, but I wasn't sure.
In general, my "i" is far forward, with an F2 frequency of about 2100Hz, but my "ɪ" was relatively far forward (around 2000Hz) but quite a bit more open (F1 of 430Hz versus an F1 of 320Hz for my "i"). I thought the most interesting thing was that I have very little distinction between "ɔ" and "ɑ"... the F1 frequencies for these were nearly identical, meaning that I guess my "ɔ" has migrated downwards to become a lower vowel, though it is actually farther back (slightly) than my "ɑ." I was wondering whether other people saw this shift as well?

Also, I played the McGurk Effect example for a couple of my friends and they were all quite surprised by the extent to which the visual cues dictate what we think we hear. One of my friends particularly prides herself on having a good ear, as a musician, and she was thrown off by the clip. I think I realize that this comes into effect for me particularly when speaking Spanish, which is a second language for me: I have a much easier time understanding someone if I can watch them speak Spanish than if I just hear it (for me, comprehension from reading is the easiest). I guess this might have something to do with the McGurk Effect, as I maybe map what I see the person saying onto what I know of Spanish.