I think the answer to both questions is no. Here are my (long-winded) reasons. [and I make no claim to be an expert -- I welcome any contradictory or critical responses]
a) Trump may well become the Republican nominee, but he'll find it difficult to win the general election. Not because Hillary is a better choice (she surely is NOT), but because Trump has succeeded in building a tremendous antipathy, even hatred, from Latinos and Muslims, and a general uneasiness and dislike among a majority of women and blacks. Yes, there are Trump supporters in all of those groups, but my guess is he's running about 35% or less approval in all those groups as a whole...and if I'm right, there is no easy way to surmount a 30% deficit in those areas (35% to 65%). At the moment, the only way I can see him winning is if there are enough Independent and Democrat gun-owners who will hold their noses, cross over, and vote for Trump.
b) Should he win the Presidency, he would have trouble working with Congress to pass legislation. I do believe he would actually try to keep his promises on a whole slew of issues. However, it will be a steep uphill battle trying to build consensus with a Congress made up of 80% establishment politicians on both sides of the isle. They hate him. I think the RINOs hate him even more than the Dem's. I'm not sure even the mighty Donald can accomplish very much until the Tea Party and other conservative blocs can dislodge the old-school politicians who care for nothing but lining their pockets and staying in office. He may be a great negotiator, but for him to win over the current members of Congress would be harder than convincing ISIS jihadists to put down their weapons and convert to Christianity. The one good thing will be that he can toss out all the Obama cabinet members and appoint some people with common sense.