uilig – (does this only refer to people/persons?…… ie… “a chairde uilig”
No. All of anything countable could be expressed by “uilig”

iomlán – (does this only refer to a place being filled up? ex… bhí an halla iomlán.
No. “Iomlán” means total. The example is wrong.

Thug sé iomlán a airgead dom – he gave me all his money
Caith sé an lá iomlán ag ól – he spent all day drinking

ar fad – (Does this only refer to a time period? ex…. Bhí sí anseo an lá ar fad.)
No. The example is fine, but can be used in other senses
Chuir mé na leabhair Gaeilge ar fad i mbosca – I put all the irish b0oks in a box

oiread – I can’t figure out how exactly to use this)
Mise ach oiread 😉 (Me neither)
Ní fhaca mé an oiread ceisteanna casta riamh
I never saw so many tricky questions

ceachtar – please give a sentence
ceachtar acu – please give a sentence

Níl ceachtar acu anseo – neither of them is here

i bfhad – seems to be used so many ways like “away from” “far” how exactly is it properly used?

An rud a théann i bhfad téann sé i bhfuaire
What continues (too) long gets cold/useless

Are there different words for “either” and “neither”? If so..what are they and please use and example of using each.
Yes. Lots!
But it depends a lot on the sentence, and the same word in Irish might be translated either or neither in English

ceachtar/neachtar is one pair.

It might help you to look up some of these words in the corpas: http://corpas.focloir.ie