The enchantment value of the Bow in MW is 7.

In sermon 7, Vivec mentions so:

'Where destines
Clothe the distance,
Glad in the golden east that we saw it now',

'clothe the distance' sounds like what Auriel's Bow does for Anu, as the Bow connects Nirn with Anu/Gods Head.

and

'...The Duke of Scamps said, 'I was summoned by Lord Dagon, master of the foul waters and fire, and I have brought the pennants of my seven legions.'...

He saw the first pennant, which commanded a legion of grim warriors who could die at least twice.

He saw the second pennant, which commanded a legion of winged bulls and the emperor of color that rode upon each.

He saw the third pennant, which commanded a legion of inverted gorgons, great snakes whose scales were the faces of men.

He saw the fourth pennant, which commanded a legion of double-crossed lovers.

He saw the fifth pennant, which commanded a legion of jumping wounds looking to hop onto a victim.

He saw the sixth pennant, which commanded a legion of abridged planets.

He saw the seventh pennant, which commanded a legion of armored winning moves'.

Is it referring to 7 walking ways? According to the context, should I say that Nerevarine is trying a complete new path to heaven designed by Tribunal, and which equals 7 itself?

As far as the Auriel's Bow connection: I don't yet understand the connection you're making, but it should be noted that Auriel's bow has changed enchantment through the games, and probably had its fairly normal enchantment value in Morrowind chosen so as to be between steel and Daedric in quality. So if there is such a connotation there, while I think you should explain it more, it's probably unintentional. Could you clarify what you mean by the bow "connecting Nirn with Anu"?

The Seven Pennants should be considered in the context of the Sermon. The basic thrust of this particular chapter is to say that no power is enough to stand before Nerevar (and ALMSIVI - since Vivec is basically writing this to aggrandize themselves). Sermon 7 describes a scamp who has all these terrifying and powerful armies to present before Dagon, but the Domo takes one look and says:

And then the next bit is about Nerevar and his fate. That's essentially it - the pennants are things that Morrowind is stronger than.

If you wanted to attribute a more specific metaphorical meaning to the seven pennants, here's what I think. They all represent historical enemies of the Dunmer people - which is why the Domo makes the point about the Hortator being stronger than them.

The first pennant commands "grim warriors who could die at least twice". This would be the Shezarrines, or specifically Wulfharth and the old Nordic empire who ruled them for a period in the First Era. Wulfharth literally dies at least twice.

The second pennant is the Alessian Empire, and possibly the Remans - Morihaus is a bull, possibly winged, and certainly the most important bovine character in TES lore; the Emperor is also a clear nod to Cyrodiil, with Reman as the "light of man" possibly being an "emperor of color" - Pelinal, associated with stars and blood, would also fit this role.

The third pennant is not obvious, but it could relate to Akavir. The Tsaesci were probably not literally as bizarre as Vivec describes them, as great snakes covered in faces, but if we're keeping with the theme of Tamrielic foes it just about fits.

The fourth pennant most likely represents the Enantiomorph in the shape of Talos. "Lovers" connotes their unity, and "double-crossed" signifies that a betrayal was involved. Also, Talos is associated elsewhere with the number four, and the fourth Walking Way.

The fifth pennant is anyone's guess - I've heard suggestions that "jumping wounds" means the Knahaten Flu; I believe it to represent the Orsimer, or perhaps the Dragon Break.

The sixth pennant is likely the Eight Divines, and the Aedra in the role of Tamrielic worship. They're "planets" because the planets literally are the remnant of the Aedra, and "abridged" because Imperial faith presents a somewhat lessened and more comprehensible version, which is only a fraction of their true divine identity.

The seventh pennant is, again, not at all obvious; I think that it's about the Numidium and the Armistice, being an "armored" god/construct that is able to win Tiber Septim his crucial battles, but causing much destruction in the process. Other mentions of armour in the Sermons that I can think of are the Ruddy Man and the Captive Sage.

But the precise meaning of each of these armies isn't really relevant to the overall meaning of the sermon, I believe.