I am going to have to hazard a guess and say no, "Lexophile" is not a word. If it is any consolation, "Lexiphile" is not much better. Neither are listed on Merriam-Webster's Online Dictionary, which you have probably already checked. Definition Of by Farlex does have a matching definition of "Lexophile" but it is noted as slang and it does not directly appear in their main Free Online Dictionary. Despite this seeming affirmation, please allow me to explain my assertion that neither is the proper word for this:
Supporting your side of the argument is the fact that most of the phobias listed on Alphadictionary's Corrected List of Phillias, do indeed have the letter "O" preceding the "-philia" suffix. Most such words, including the more commonly recognizable ones like "Pedophilia", already had an "o" to begin with, like but some of the others recognized, like "Textophilia" do seem to simply append or just remove some letters to make room for the "O." Despite seeming applicable, a "Textophile" is just somebody who has a love of certain fabrics, and hence is presumably derived from the word "Textile". It is quite an extensive list and while there are a few Philias ending with other letters, the letter o is usually connected to this suffix. However, despite being preferred it is not strictly required and forms are connected with other vowels. Skimming through the list, it does seem more like a rare exception, rather than the rule.
There is more to it than just that though. A wildcard search of A.R.T.F.L. Project's transcripts of Webster's 1828 and 1913 Dictionaries on The University of Chicago's website does not even show any words starting with "Lexo", let alone ones which fit the context. Meanwhile, all of the words in those dictionaries starting with "Lexi" pertain to words. The only word "starting" with the l-e-x combination of letters, which isn't within the "Lexi-" category is "Lex" itself, meaning law in Latin. Few if any people are going to recognize the prefix without the letter 'I'. The last example word so far, clearly demonstrates why "Lexophile" would not work: By virtue of the word's construction, the most likely assumption made by your fellow wordsmiths may be that you're referring to a workaholic attorney, which necessitates an alternative:
Alphadictionary's list actually suggests "Verbophile" and "Logophile" are acceptable. "Logophile" has the advantages of being noted as the preferable alternative by the list and also appears in Merriam Webster's Online Dictionary, unlike "Verbophile", suggesting it's already adopted. I do not particularly like "Logophile" myself though, since it seems more like a lover of corporate trademarks in this contemporary era, rather than what its definition suggests it actually means. It also lacks that resonance with the word "Lexical".
To the end of finding a more appropriate word, there is also one other common thread that my earlier wildcard search revealed, which is somewhat conducive to our purposes. Most words starting with "Lexi-", excepting "Lexical", "Lexigraphy", "Lexiphanic" and their variants have a couple of other letters appended to the end. The only surviving one of those exceptional word families presently in Merriam Webster Online is "Lexical". Out of these three words, only one appears in Webster's 1828 Dictionary and its "Lexigraphy", which gains its eventual replacement spelling in the 1913 dictionary that is more consistent with the other words
[Sidebar: Through coincidence, I also know a certain Children's Card Game that has a "Lexivore" but Magic: The Gathering probably isn't a good source for actual words, especially if you're trying to pull them out of sets of the unofficial joke card sets. The monster may have also just gorged some of the letters out of its own name...]
So by use, "Lexi-" as a prefix seems more common but it is falling into disuse. There is actually a very good reason for that. The proper prefix pertaining to words isn't actually "Lexi-" but rather it is "Lexico-", or at least that is the only one listed in The Online Etymology Dictionary. "Lexical" probably just dropped the "O" to avoid having a double vowel that makes it sound like lexicoal, the fuel of choice for Reverend Lovejoy's Book Burning Mobile. Putting the jokes aside, if we're going to make a neologism for this, the most proper and linguistically consistent word would be "Lexicophile" (Definithing.com). Aside from being the full prefix, it also ends in an "O" to transition into the "-philia" suffix.
Unfortunately, regarding dates, Google Ngrams does not recognize any of this subject's three primary word choices on this matter, nor does The Online Etymology Dictionary regardless of whether I search for "Lexi" or "Lexo". I have no idea where else to look for clues unfortunately.