Ravnica Allegiance Prerelease Strategy Puzzle

There was one play at the prerelease where I think I should have made better decisions to win the game, but I can't figure out what was the best line.  I've been puzzling on it a lot.

Opponent was Rakdos and I had just allowed him to attack for 9, dropping me to 8, because I was planning to win on my turn.

My hope was that he would play a creature and I would know what to play around on my turn, but he didn't.  So here is what I saw after drawing the Plains:

As you can see, I had enough mana to cast Biogenic Upgrade and also activate the Courier's vigilance ability after playing my land.

What actually happened:

I played Biogenic Upgrade, put 6 counters on Senate Courier, then played the plains, then activated vigilance, then attacked with everything.  He cast Get the Point on the 7/10 Senate Courier, took 4 damage, and won on the backswing.

I had not seen Get the Point in the first two games of the match, so I didn't have any specific reason to think he had it other than that it's a common in his colors.

There were really 2 decision points here.  The first was what to target with Biogenic Upgrade, and the second was how to attack (knowing that he already hadn't cast removal in response to Upgrade).

My thinking included the following:

• I wanted to make a lethal attack and avoid letting him have a next turn.
• I wanted to avoid getting blown out by removal in response to casting Biogenic Upgrade.  For example, Flames of the Raze-Boar would have been a bad 2-for-1 for me.  I don't think I was specifically thinking about Flames of the Raze-Boar in that moment, but I was generally trying to reduce the chances that a 2-3 damage removal spell counters part of my Upgrade.
• I wanted to play around cards I had already seen, which included Scorchmark and Spire Mangler.
• I wanted to be able to block his 6/6, preferably with a lethal block, if he had something like a flash blocker or a lifegain spell.
• His topdecks are mostly better than mine since black-red has aggressive cards including haste and direct damage.

He was smart to hold his Get the Point until my attack without giving away that he had something.  At that point all I knew was that he didn't have a removal spell that only kills the owl when it has 4 toughness (damage-based or -X/-X).

In hindsight, which is 20/20, I would have won if I had spread the counters from Biogenic Upgrade onto the 3 creatures with 1 power and attacked with everything.  This would have given me 3 + 3 + 3 + 2, and with his Get the Point, the best he could have done was get the attack down to 8 damage.  I think this was a pretty good plan overall, because the only spell I can think of that beats it outright is Flames of the Raze-Boar.  If he had that card, he would have been pretty close to winning outright, because I would have had to plan to chump block with the afterlife creature (attacking with the Gateway Sneak if it was clear) for two turns and hope my topdecks were better than his.

Another possibility would be to put 2 counters on the Courier and 4 on Gateway Sneak, which is better against specifically Flames of the Raze-Boar.  That allows for an exact lethal attack without tapping the afterlife creature or the Faerie, and has better implications against removal.  Maybe that's the best way to cast Upgrade in this situation.  Worst case, he kills the Sneak and Faerie with Flames of the Raze-Boar, and I have a 3/6 vigilance flier and a 2/3 afterlife flier, which is maybe enough to chump block and close the game in 3 attacks.

Finally, 4 counters on the owl and 2 on Sneak is also a reasonable choice, because it sets up the owl to block the Ruin without exposing the board to single removal as badly.  Then, I attack the owl and the Sneak, as above.  Having 2 blockers back including the afterlife bird to trade with the Vandal would have been reasonable.

Now, what should I have done differently on my attack, after Upgrading only the owl?  I'm not sure that there is a great plan.  In hindsight, I always want to attack with the owl and he always kills it, which leaves me in mediocre shape regardless of the rest of the choices.  Assuming I leave back the afterlife creature, which is the second best blocker, I am attacking for 2 after the owl dies, then chump blocking and hoping to do 6 more damage off topdecks.  If I leave back the Faerie instead, I'm attacking for 3 after the owl dies and hoping he doesn't have a small removal spell like Scorchmark on his turn.  Granted, the Gateway Sneak draws me extra cards, but none of these attacks is a super plan even with Angel of Grace somewhere in my deck.

My conclusion is that Upgrading only the owl was the point where I should have made a different choice, and I should have spread the counters around in one of the above ways.  In any situation where he isn't holding a single-target removal spell, it would have almost certainly won the game, but so would spreading the counters.  What's the best spread?

After Upgrading only the owl, I think my best attack is everything but the Faerie, which presents 10 damage and draws a card and leaves me with a big blocker and a small blocker if they all live, or a small blocker and 3 damage if the owl gets removed (as it did).  I can't think of any instant speed ways he could have gained life, but there are several ways he can live through the attack (including the Get the Point that he actually had).  It's not great, but  I think it has the most upside.

My downfall, as often happens, was playing toward the fastest win and not analyzing the implications of the possible answers they could have.  Because of the different styles of decks we were playing, I still think I want to reduce the number of turns he gets to draw, but there were safer ways.

What do you think I should have done?