Marginal sanctions relief on a step by step basis with substantial concessions from the North on denuclearization, allowing inspectors to verify denuclearization steps, etc., is a way to proceed with negotiations.
The sanctions waivers that South Korea needs to reopen Kumgansang, and Kaesong are a good starting point. The North needs to deliver to get those.
The North doesn't really have any hard and set demands regarding US troop withdrawal, that issue concerns the deployment of "strategic assets," like aircraft carriers, nuclear submarines, and long range bombers. The US has a nuclear strike capability that can reach anywhere in the world, with or without the visibility of such assets in the immediate region.
Conducting massive military joint military exercises in their neighborhood is obviously a reason for them not to denuclearize and US military leadership understands that as well.
The notion that South Korea might have objected to the suspension of joint military exercises by Trump after the first summit is absurd. This is what the South Korean administration wanted.
There is an inherent conflict between maintaining the greatest possible sanctions and proposals for normalization of relations with the US. These kinds of contradictions are typical of US Asia policies in which the left hand doesn't like what the right hand is doing.
Linking denuclearization negotiations to human rights issues in North Korea is another formula for failed talks. The idea that lobby groups in the UN and the US, and political opposition in Korea itself care or know more about human rights abuses or what to do about them than the current administration in South Korea is off base as well.