I like these questions and thinking about them.
I am always attracted to animal predation theories, because somehow I got into studying animal-human interactions in the wild. But, in this case, I do not think that happened. There would in fact be signs of that.
I'd add one scenario (suicide). However, it has some of the same difficulties as the animal attack theory. She would have been found by now.
SO, it's either a murder or an abduction (followed by who knows what).
Now, to question 1. It's possible LE is following a couple of theories as this unfolds. We won't hear anything about any of them. But if they suspected an abduction by a person outside the immediate area, they would surely alert the public. So far, they must not evidence of that, but instead many other leads that are local that they are still following. Since we don't know exactly what LE has done (but I believe they've made an effort to talk to nearly every adult citizen of the Salida/Maysville area), it's hard to know what they would change. As far as we know, they haven't searched any residence except the Morphew residence. Could they have found evidence that shows Suzanne had relationships outside Salida that could have something to do with the case? We wouldn't know. The FBI actually knew that Letecia Stauch had gone along a certain route leaving Colorado and field offices all along that route were alerted or otherwise involved in that case. They knew she was going to return a rental car on a certain date and were there to intercept/arrest her so as not to do it at the residence she shared with her daughter and so as to have an element of surprise and avoid any suicide or homicide attempts.
So, if there is a viable "other suspect," LE has done nothing to indicate that, they've only focused on BM, as we all know. But there could be other suspects.
2. This is just basically asking our opinion on what we think we would do if our spouse went missing and the differences that we see generally between people who end up being found guilty and those who are not. If I truly had no idea what had happened, I would certainly consider "animal attack" and would put all my resources into trackers and animal behavior experts to rule that out. If I thought it was abduction, I'd rent a billboard (as has happened in other cases of this type where the family/community has resources to do so). If local laws forbid that kind of signage, I'd have detailed posters (like the ones we often see here for missing people) with every bit of information I could get out. I'd be at his last known location searching, daily, and would organize searches myself. I would have USGS maps of the region, I would use parts of those maps to engage people in more searches.
I'd cooperate as fully as possible with LE (through an attorney, for various reasons) and I'd expect LE to give me details such as exactly where they searched, so that I could continue searching once SAR teams were done with their thing. I'd be at the actual police station daily and I would expect the head of that organization to meet with me regularly or I'd be going as wide as possible with my criticism of local police (for their failure to see me regularly, I would not expect to know everything, but I would expect regular contact). If my husband disappeared on a local bike trail, I'd personally talk to as many bicyclists as possible, hoping they'd see a clue. I would have a website devoted to what I found. I'd be here on WS asking for help. I'd be everywhere I could be, asking for help. I'd raise money for one of those smart drone searches (I probably would need to, not sure we could afford it on our own).
If he was missing for a month, I'd need to memorialize the last spot I thought he was by leaving some flowers, getting together with family at that spot, probably inviting the community to that spot after a couple of months. I think by then, if LE had turned up no evidence of foul play, I'd consider his disappearance to be a wilderness misadventure, and I would continue to ask help from locals who frequent the backcountry. But my posters would use every bit of digital data at my disposal to give possible searchers an idea of where my husband went missing and what his typical habits were. LE would not be able to stop me from doing that. Naturally, I'd give LE all the information I possibly could.