In no particular order:
For text apps: I recommend Handcent (though I've never used eztext). Simply replace the Messaging shortcut with the Handcent one, that problem is solved (or at least that's what I did).
For Verizon breaking the texts: After a certain size, the default text app sends it as an MMS instead I believe. If not, it just splits it up, in which case other verizon users will receive multiple texts, and non-verizon users will have varying results. I've had non-verizon users get combined texts and I've had them get only the first half. I *think* handcent splits them up automatically and sends them separately.
Texting multiple people: So, when I go into texts, and hit new message, and click in the To: box, I can start typing in a name. When I do, suggestions pop up underneath, I press the one I want, their name and number show up (ie John Doe <555-555-5555>, ). Click back in the box after the comma, it lets you type in more names, same process, repeat. Clunky, but the function works. If the comma doesn't show up for you, try typing one in yourself.
I hope this is a little more helpful.