Reenter the US on VWP [duplicate]

You left the US and now you're returning. This is, by definition, a second entry. It's very unlikely that you'll be given a second 90-day admission, unless the immigration officer is half-asleep.

Remember that the officer must assume that you're going to become an illegal immigrant unless you can convince them otherwise. When you return to the US only a few days after making a long visit, their immediate suspicion will be that you're trying to spend more time in the US than you're allowed to under VWP. The only way you can counter this suspicion will be to strenuously insist that the story you told when you first entered the US was true: you've always planned to leave on that flight on April 5th but, for whatever reason, you decided to spend a couple of days in Colombia before then. And, since you're so insistent that you'll leave on April 5th, they don't need to stamp you in for another 90 days, right? Until, say, April 7th should be fine, yes? Just in case something goes wrong and you miss your flight.

Alternatively, the immigration officer is half-asleep, you get your 90 daysand use them, and then, the next time you visit the US, and you get to face the music about "Oh, so last time we let you in, you were basically here for six months. What's with that?"

As mentioned, I did read a lot about this and I am aware of the risks

You're clearly thinking this is doable at all. I'll tell you right now: forget it, it's doomed from the very outset.

What you want to do is a textbook visa run, and the US authorities don't tolerate that. On a single visit you're meant to spend no more than 3 months, and exiting for only a few days hardly counts as ending a visit in terms of intentions.

Think of it this way: how long do you intend to stay for at once? 6 months in your case, which is why you don't qualify for the VWP.

So get that flight back home on 5 April, and, after this 3-month visit, stay away from the US at least for another 3 months (not a formal requirement, but a good rule of thumb in practice).

If you really wish to spend half or even most of the year in the US, get a B visa from the US embassy. Bring solid proof that you can support yourself and that you have to return home, and have a good idea of what you wish to do.

With a B visa you can stay for up to a year (though usually subject to a 6-month extension)