Remus didn't see the "number", but the "birds", so the antecedent of the relative pronoun is avium. The form should therefore be quas (acc. pl. f.).
(BTW the irregular nom. pl. of deus is more commonly spelled di, though dii apparently occurs too.)
The usage of plus and other forms like plures, plura seems to be a little complicated and depend on the grammatical number.
Plus can be used as a singular noun or an adverb
The form plus looks like a singular neuter adjective in the nominative/accusative case.
However, what I've read is that this word in the singular is only used as an adverb (the nominative/...
As Cerberus points out, plus is an adjective and has therefore the gender and number and case of the main word.
There is also the corresponding adverb plus, which could be seen as the neuter accusative of the adjective.
The word magis is also an adverb, but not synonymous with plus.
I assume your question concerns the adverbial usage, but do bear in mind ...
The adjective plus means "more". If you want to say more than, you can either use the (often elliptical) conjunction quam, or an ablative of comparison.
[Ego] habeo plura capita quam homines [capita habent].
[Ego] habeo plura capita quam [ego habeo] caudas.
After quam, you would use the same case as the first element of the comparison, so ego ...
Hello and welcome to the site!
punituri: The future participle must agree with its subject, so it should be deos punituros
potuisse: As pointed out by Jasper in the comments, this is a subordinate clause and as such should be rendered in the subjunctive according to the consecutio temporum (c.t.). It depends on the nearest finite verb, dixit, and describes ...
According to Vester (1991; see the full reference below), the gerund can take an object in the following contexts:
genitive: ars scribendi (epistulam)
ablative: scribendo (epistulam) tempus tero
nominative: mihi (epistulam) scribendum est
According to Vester, "it is evident that scribendum is a gerund in mihi epistulam scribendum est, but for some ...
Some common rules seem to emerge: avoid hybrid words, use connecting vowels in compounding, chose the specifically appropriate word(s) to adapt, there seems to be a preference for compounding (unsure about this), and the Vatican seems to prefer phrases to compounds as do others.
It seems that hybrid words may not be preferable in Greek and Latin neologisms, ...
Nemo est qui... is a common enough formula in Latin, "there is no one who...". Since nemo can be used with est there is no reason it cannot be used with sum.
Indeed the phrase nemo sum homo is attested. See here.