1) Emphatically no.
Trump is no more a Republican than is Ted Cruz a Democrat. Trump has given about eleven times more money to democrats than to republicans in his adult life according to an analysis run by National Review. Trump supports a variety of positions that just about every likely voter who self-identifies as a Republican would loudly oppose save, perhaps, for the least informed among them. Single-payer/universal healthcare, significant restrictions on gun ownership rights, large taxes on business, tariffs on China and other competitiors, bloated farm subsidies and other boondoggles, the abusive use of eminant domain for personal gain, and, perhaps most importantly, partial birth abortion and the continued federal backing of Planned Parenthood. The fact that he has reversed himself miraculously in 2015/2016 on some (but not all) of these issues is quite opportunistic, but I don't frankly buy it. Note, also, I am not a Republican, though I am conservative. I don't agree with the GOP on all of the issues I outlined above, just noting the issues that he's taken the opposite side to the GOP platform on...and they are quite numerous.
2) The GOP is not now, nor has it ever been, truly united (but we could say the same for the democrat party - our two-party system forces each side to form a broad coalitiion of constituents and appeal to them as often as they can without alienating any of them). While democrats hold a coalition that sometimes forces leaders to choose between the priorities of blacks and Hispanics (they sometimes collide), greens and union leaders (they almost always collide), and educated elites and uneducated (disenfrancised) minorities (they conflict more than people seem to realize), the GOP is basically broken into four groups. Religious populists (whose main issues are social - right to life, anti-gay-marriage, anti-poverty family programs, etc), small and moderate-sized business (big business leans overwhelming to the left these days because a big government benefits large businesses and crushes their competition) owners and investors (the club for growth / chamber of commerce side of the party) whose main issues are deregulation, GDP growth, and taxation, the libertarians, who vote about 2 to 1 for the GOP and who are primarily interested in small government and constitutional rigorism, and constitutionalists/tea partiers (some in the te aparties are really religious populists, but many are hard-line constitutionalists with just a flavoring of culture warrior on top) whose primary issues right now are illegal immigration, the rule of law and fears about the government becoming abusive or toxic to individual liberty.
Having said all of that...there is one issue that unites conservatives today - even the libertarians. That issue is radical Islamism. While the left seems desperate to accommodate and adjust to the encroaching of Islamist calls for tolerance that seem highly one-sided (as in...we are asked to accept their way of life, but they demand we change ours), the right seems united, today, in its desire to fight Islamism (there are disagreements on the best way to do this). Note, I'm saying Islamism, not Islam. They are not the same thing - something I wish Trump would recognize.
3) No, I don't think every conservative would agree on the most important issues.
The net average, right now, would favor security-based issues - Islamism and Military strength, illegal immigration, federal government lawlessness and the infringements of our Constitutional rights that many perceive are underway...and that our economic concerns, which used to be near the top of our list, are, at present, lower down.