Re who/whom: Yes, I’m sure. You can test it by inverting the word order and substituting he/him for who/whom. You would not say “close to he,” you would say “close to him.” Thus do not use who, use whom.
For the lie/lay situation, it helps to know the principle parts of these verbs.
For lie (=recline), they are LIE, LAY, LAIN. I like to lie in the sun. Yesterday I lay in the sun for hours. I have lain in the sun for years.
For lay (=place), they are LAY, LAID, LAID. I lay my clothes on the bed each morning. Yesterday I laid my new shirt on the bed. I have laid my clothes on the bed for years.
The confusion comes from LAY being used for the present tense of “lay” and for the past tense of “lie” combined with 80% percent of the population (including professional copywriters and scriptwriters and broadcasters who should damn well know better!) using LAY when they should use LIE.
In your examples, both sentences are in the present tense and lies/lie are correct. So:
“The perfect blue sky surrounds me, and beneath lies intensely vivid, green earth.” But if we shift to past tense, it would be: “The perfect blue sky surrounded me, and beneath lay intensely vivid, green earth.”
The second sentence has an additional problem: “When looked at from the right angle, I can…” is saying you can do whatever when YOU are looked at from the right angle. This is more obvious when we shift the word order a bit: “I, when looked at from the right angle, can…”. What you want here is “Looking at the right angle, I can…”. (To simplify the illustration, I’ll use “see” instead of “can see.” “Can see” is fine, and its past tense is “could see.” I just thought it clouded the tense recognition a bit.)
“Looking at the right angle, I see past the reflections and into the shallow river’s foundation, where countless rocks lie, each of a slightly different color.” And then in past tense: “Looking at the right angle, I saw past the reflections and into the shallow river’s foundation, where countless rocks lay, each of a slightly different color.”
When in doubt, use RECLINE or PLACE to determine whether you need LIE or LAY, then use RECLINE/RECLINED (or PLACE/PLACED) to verify which tense you are using. Then if you know the principle parts of the two verbs, you can select the right word to use.