John 3:16-21 Translation

16. For God so (in this way) loved the world, that (so that) He gave the only (unique) son (or the son the only begotten) in order that all who believe in him might not (should) perish but might (should) have ever lasting life. One note hoste and the indicative classical construction of practical result. Used here and in Gal.2:13 only in NT. Note the subjunctives
17. For God did not send the son into the world in order (so that) he might (should) judge the world, but in order that the world might be saved through him.
18. The one who believe in him is not judged. But the one who does not believe is already judged, because he has not believed in the name of the only begotten son of God.
19. And this is the judgement that the light has come into the world and men loved the darkness more than the light. For (because) their works are evil. 
20. For everyone who does evil, he hates the light and he does not come to the light, lest his works convict him.
21. And the one who does the truth comes to the light, since his works may(might, should) be shone that they are works in God.


Questions: 
1. Why are the perfects in verse 18 translated in the present?
2. How did you translate  i”na mh; e∆legcqh≥: in verse 20?
3. Did you feel like or see the need for "His son" in verse one?
4. Are there any variant readings?