@emacarea
FilipinoChatAdmin and Daoxin have already given you the right answers to most of your questions.
With regard to spellings, there are standard and correct ways to write Filipino words. It's not a case of spell-it-any-which-way-you-want, which is only OK with texting for the sake of economy. There may be slight, but acceptable, variations with some words like “buwisit” and “bwisit” or “puwede” and “pwede”. Mostly they are the result of omitting a letter, which would not have a noticeable effect in the pronunciation of the words anyway.
In the case of “lalaki” and “lalake”, the original and supposedly official spelling is “lalaki”. The strange thing about it is, the way we have been pronouncing it is closer to “lalake” than “lalaki”. Maybe that’s because pronouncing it as “lalaki” may be confused with the future tense of the verb “lumaki”. It is possible that there are those who would spell it now as “lalake”, but those who know Filipino well enough would understand that it’s not really the proper way to spell it.
Another example is “bakit”, which we usually pronounce more like “baket”. However, I have not seen the word spelled as “baket” yet, unless perhaps when someone is trying to be funny.
There are some areas in the Philippines where they tend to mispronounce the vowels “e, i, o, and u”. It used to be that local comedians use it as a tool to elicit laughter, but that’s before the ideas of political correctness and racism were taken into consideration here. Now, only comedians from those areas can get away with it for the reason that they are just being themselves and be naturally funny for being so. Just last week, a respectable blogger pointed out that our president said, ‘the communists are engaged in “armed stragol” ‘ during a nationwide TV broadcast. Some Visayans were offended by her comment that she had to apologize for it.
Maybe the Filipinos you’ve been dealing with are from such areas and that’s why you arrived at this idea that “e” and “i” are interchangeable. However, if you’d ask them to spell the word, they would most likely spell it the right way. They just couldn’t help but pronounce it the other way.
I sometimes hear native-Spanish teachers advise native-English learners to learn how to roll their “R”s. I also know that some English speakers struggle with how to pronounce a Filipino word like “ngunit” correctly. I think it’s the same thing with those Filipinos who have “problems” with their “e, i, o, and u”.
So, it seems that we are confusing pronunciation with spelling. Going back to "bwesit", you should realize that I understood the word you used even if the spelling is not how it should be. If you've been hearing people pronounce "bwisit" as "bwesit", and be led to think that that's how it should be pronounced, then we can't do anything about that. However, my point only was for you to know the proper spelling of the word so that if you hear someone pronounce it as "bwisit", then you'd know that that's really how it should be.
The Dictionary on this site provides audio guides in pronouncing words. When in doubt, follow the audio guides here as they would be the proper Filipino pronunciations of the words.
I am sorry if you consider my interest to help you learn Filipino properly as rather offensive. I'd be extra careful next time.