1. Are there members outside the Philippines? Where and how many? Any in the U.K. For example.
Yes, there are members. It is unknown how many members since the church doesn't publish member numbers.
2. Have JWs and the Iglesia ever discussed or acknowledged each other in literature or otherwise?
JW's discussing INC: Not that I am aware.
INC's discussing JW's: Yes. There are a few videos even of people who were JW and converted to INC.
https://www.youtube.com/watch?v=fPd7GguO1cE
3. How did they arrive at 1914, with the same WT chronology or another method?
The INC sees 1914 as important because it was the year in which the religion was established. Different reasons for holding the year as special, but same end result: 1914 was the beginning of the Last Days.
http://theiglesianicristo.blogspot.mx/2013/02/iglesia-ni-cristo-why-only-1914.html
4. When was their best period of growth? JW/BS have been around since nineteenth century, but their growth before 1945 was slow. Is it similar for the Iglesia.
No idea.
5. What is the proper short way of referring to them? Iglesia?
INC I believe.
6. What Bible translation do they use? Since the NWT would probably fit their needs better than mainstream translations.
They use various as needed. They use Moffat's translation to prove that Felix Manalo is the Last Messenger.
Isaiah 43:5-6 in the Moffat version is specially useful to them:
He will call from the Far East in these last days.
Far East: Phillipines.
Last days: Starting when he calls in the far east... i.e. Felix Manalo, from the Phillipines, in 1914.
7. Are they still growing or in decline?
No idea. Probably still growing.
8. Have they received support or persecution from the government?
HUGE support in the Philippines. Because they vote, and more importantly, because they block vote, they are an important political tool. So I guess there is lots of quid pro quo going on.
9. Do they have a Memorial celebration?
Good question. Not sure.
10. How does their structure compare with JWs? Elders, circuit overseers, governing body, assemblies, congregations?
Very similar.
According to: http://www.watchman.org/profiles/pdf/iglesianicristoprofile.pdf
Organizational Structure: The group is hierarchical in nature with ultimate authority resting
in the Chief Executive Minister (CEM), Eraño Manalo, the son of Felix Manalo. A Church
Council of 17 executive officers oversees church matters and issues tagubilin or circulars
that cover everything from personal behavior to approved political candidates.
11. Do they preach and how?
Not sure.
12. Do they use Jehovah's name or say it is important?
No, see below:
https://iglesianicristoreadme.blogspot.mx/2011/12/is-name-of-god.html
13. Do they teach a paradise?
Don't think so.
14. Do they say the "end is near" now or have any prophecy to back it up?
Yes. 1914 was the beginning of the last days. Their eschatology is quite convoluted like the JW's. They try to interpret Revelation in modern times.
15. Are they creationists? Young earth or old earth?
Young Earth Creationists, see:
http://theiglesianicristo.blogspot.mx/2015/06/is-evolution-scientific-and-will-person.html
16. What's thier views on sex and homosexuality?
Pretty much identical to JW's. Wrong.
17. Is there a big community of former members?
Yes. There is a "jwfacts" for them, mentioned in the article.
18. Any good books on the subject by former members or academics?
Not that I know of.
19. How many numbers are these questions going to go up to?
Too many.
20. What prompted your interest in the subject?
Filipina JW girlfriend, she mentioned them to me years ago...