Death Ward will trigger the first time you drop to 0 hit points, and Relentless Endurance won't. Then next time you drop to 0, Relentless Endurance will be ready to go.
Death Ward, emphasis mine:
The first time the target would drop to 0 hit points as a result of taking damage, the target instead drops to 1 hit point, and the spell ends.
As soon as you would be reduced to 0 HP, you are instead reduced to 1. As opposed to the Relentless Endurance trait, emphasis mine:
When you are reduced to 0 hit points but not killed outright, you can drop to 1 hit point instead. You can’t use this feature again until you finish a long rest.
You choose when to use it. It doesn't automatically trigger when you are reduced to 0 HP. So when you are reduced to 0, with both Relentless Endurance and Death Ward, just don't use Relentless Endurance. Death Ward will be used, then next time you drop to 0, you can use Relentless Endurance.
There's another point to be made here, though. Even if you want to use Relentless Endurance, while you have Death Ward on, you can't.
The first time the target would drop to 0 hit points as a result of taking damage, the target instead drops to 1 hit point, and the spell ends.
Death Ward triggers when you would drop to 0, and makes you drop to 1 instead. You never actually drop to 0.
When you are reduced to 0 hit points but not killed outright, you can drop to 1 hit point instead. You can’t use this feature again until you finish a long rest.
Since Relentless Endurance is triggered when your hit points are reduced to 0, and Death Ward prevents you from ever reaching 0, you couldn't use Relentless Endurance even if you wanted to. This argument also works if your DM believes you don't get to choose when to use Relentless Endurance, which you asking this question suggests he does.
Yes, Divine Smite will work while Wild Shaped. Wild Shape allows you to use your class features:
You retain the benefit of any features from your class, race, or other source and can use them if your new form is physically capable of doing so.
And Divine Smite works like this:
Starting at 2nd level, when you hit a creature with a
melee weapon attack, you can expend one paladin spell
slot to deal radiant damage to the target, in addition to
the weapon's damage.
Divine Smite requires a melee weapon attack. Every beast type creature that I can think of has at least one attack that is a melee weapon attack. For example, the Wolf:
Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target.
Hit: 7 (2d4 + 2) piercing damage. If the target is a creature,
it must succeed on a DC 11 Strength saving throw or be
knocked prone.
So you can use your Divine Smite with the melee weapon attacks provided by your Wild Shape form.
Best Answer
RAW, you are dead
Xanathar's Guide to Everything states you move 500 feet in the first round* of falling. If you fall anything between 200 and 499 feet, you take 20d6 damage, and don't have time for Wild Shape.
Your DM can save you
Based on your question, your DM is willing to let you use Wild Shape while falling.
Dire Wolf is not enough, you will need a form with 110 - 2 x 34 = 42 HP. There are 2 of these in the official sources:
If your DM lets you take any of these, you not only survive, but you can walk away thanks to Relentless Endurance.
*) This is pretty good physics for the first round. Unfortunately for subsequent rounds it still sets your speed to 500 feet per round, while it should be closer to 1100.