actually its not, since we have many problems with this model. also: unless you believe in a theistic evolution, there are no small steps between many different creatures.
as for the age of the earth: first: i never said i believe in a young earth. i just say that we dont know what is the real age of the earth. but i will try to deal with your points:
we have two possibilities: human population was to small to leave fossils, or human was created after dinos (mean several creations events).
actually i think that the opposite is true. for instance: we have empirical evidence that speciation may take about less then 100 years:
http://discovermagazine.com/2015/march/19-life-in-the-fast-lane
so lets assume a tipical speciation event= 100 years.
one of the largest family on earth is the curculionidae which contain almost 100,000 species. so if we start with 2 species then after about one generation of a speciation event (100 years) we will get 4 different species. and after another generation of speciation we will get 8 and so on. so we only need about less then 20 generation of speciation to get more then 100,000 different species (2^20) . or about 2000 years.
so we can explain your main two objections without an old earth.