2. English vowels front central back high i u   mid e o E   low  A 
North Atlantic English (UK, Ireland):
front
central
back
unrounded
rounded
high i u
lower-high  
mid
higher-mid e o
lower-mid E  
low  A 
Quantity and quality are interrelated in English. It’s true that the high vowels are longer and more peripheral in the vowel space than the lower-high. And this is also true of [e] vs. [E] and [^], but not really true of [o] vs. [O].

3. English vowels A speaker from Southern England: lower-high lower-mid
front
central
back
unrounded
rounded
high
[bid] bead
[bud] booed
lower-high
[bd] bid
[bdst] Buddhist
higher-mid
[bed] bayed
[bod] bode
lower-mid
[bEd] bed
[bd] bud
[bd] bawd
low
[bd] bad
[bAd] bard
[bA] bah
[bdi] body

4. English vowels Sound changes in N. America. What happened to []:
,  > (‘merged as’)  (East)
[]: body, bawd, []: bah
,  >  (East, Midwest)
[]: body, bah, []: bawd
, ,  > A (West)
[]: body, bah, bawd
[] was historically a lax vowel. [] and [] were historically tense vowels. When [], [] merge, is the result a tense or lax vowel? This is why the tense/lax distinction breaks down as a result of dialect-specific mergers.