The fluids get easier as you go along, becoming more comfortable with them will boost your confidence.
Those are all great numbers for Merrick
The Wellness canned & Evo are also grain free so that is a big part of the recommendation there, cats being carnivores have little - no need for grains in their diets.
My girl never liked any of the Merrick flavours, possibly too much extra veggies & stuff for her tastes
So I couldn't give a "personal" go ahead without the actual numbers.
Most of the recommendations you will see are ones that have worked for others or because the nutrient analysis is known for the foods. The list has just recently been updated where the previous one I believe was 3 years ago, so one can't recommend with outdated numbers, unless one has contacted the company directly.
Good for your dh making a feeding station