2 - "ú-vedir" would rather mean "(they) cannot eat", as Tolkien says (after stating his dislike towards using √U for negation and choosing √LA) here:
The nuance will remain important. úchebin will mean not 'I do not keep', but 'I cannot keep'.
4 - lhûg does not necessarily mean "dragon". That meaning was only given in 1940 drafts, whereas all Post-LotR works gloss it as "reptile, snake, serpent, worm". The root of this word, which is √LOK, simply means "bend, loop", so arguably lhûg can be used with any thin and long creature (without limbs). It even applies to hair: loch "ringlet" < LOKko, also Q. lócë "curl of hair" & Q. locin[a?] "bent".
4.1 - The plural of hwand should not be "hwaind" because its final consonant cluster (i.e. -nd) would prevent I-intrusion. So the plural should be hwend (cf. parf > perf [not "pairf"], cam(m) > cem(m) [not "caim"], anfang > enfeng [not "enfaing"]).