Ipeaco, because your questions are so fundamental and important, I'd like to cover them as well, though FF's response was thorough and cogent. Perhaps the more of us who share our personal solutions to (or struggles with) these admittedly sticky problems, the more folks will be able to fulfill the great commission---being witnesses to what Yahweh has done for us. For clarity, I'll repeat your questions...
1. Do you still meet with other believers who don't have a clue about most of this stuff? If so, do you sing songs with 'Jesus' and 'the Lord' in? If so, how does it make you feel? Yes, I do. I feel that "not forsaking the assembly of ourselves together" is a crucial step in the spread of truth. Don't expect your fellow believers to know what you know, however. Most people you'll meet in "Church" have never been exposed to anything there that forces them to think analytically, and they've never been given a reason to suspect that what they've heard there all their lives isn't all there is to know. Learning otherwise can be a shock. So be gentle with them. Don't be offended when people use the name "Jesus," or call Him "the Lord." They don't know any better, and neither did you a while back, I'll wager. In the interests of unity and picking my battles, I don't alter the songs on the fly, but since I get to sing backup vocals in my congregation's praise band, I have the unique opportunity to use Yahweh's name in counter-parts or obligatos. (We're pretty loose and free, musically. That won't work everywhere, I realize). In my conversation with folks, in public prayer and private discussions, I never mention "the Lord" or "Jesus." It's always Yahweh and Yahshua. Clarify if you have to, but when the divine names are on your lips alone, use the genuine article.
2. Have you spoken to any non-believers about any of this stuff (i.e. names, the law, feasts, timeline etc..)? If so, how did they react? How can you expect someone to understand relativity or quantum mechanics if they haven't been introduced to 2+2=4? First things first. First introduce them to the fact of their sin, the reality of the God from which that sin separates them, and the means He has provided for reconciliation. If they haven't reached this stage expect one of two things when you bring up the subject---an argument, or a blank stare. Spiritual things are spiritually discerened.
3. How do we share this stuff with Chrisitans who already think they know the fundamentals and how can we achieve unity if we are dividing over such fundamental issues as the name of God? I don't know if this is a universal phenomenon, but it's been my experience that if a supposed believer is reticent to use the name "Yahweh" instead of "The Lord," he may be having relationship issues himself. Gentle encouragement should be all it takes to break years of habitual mis-usage. (It did in my case, at least.) Even my pastor calls God "Yahweh" now, though I never got in his face about it---I just used the Lord's (just kidding) name in conversation for a year or two. Yahshua (or worse on English-speaking lips, Yahushua), strangely enough, may be a harder sell, simply because the transliterated transliteration "Jesus" has so thoroughly permeated our language. It's not like "Yahweh," which everybody seems to realize intuitively is a substitution, not a name. And what about the other earth-shaking truths that Christians universally ignore (like the miqrym, for example)? I find that a little wide-eyed enthusiasm will get your foot in the door with genuine seekers after the truth, folks with a Berean attitude. Pretenders and posers, of course, will hate your guts for even bring it up. Sigh.
Anyway, try to remember to be humble in all things. It's only by the grace of God that we may know one iota more than the next guy. And there's always somebody out there who can show us a thing or two. Pride is the most destructive trap into which we can fall. Like I wrote somewhere, there's no particular reason the Heavenly Gardener should esteem one of us garden slugs above another. Grace is the only reason He doesn't salt us all down, the best and worst alike, 'cause let's face it, who can tell the difference?
kp