Hi @Jolly Boys,
I made a quick (and smaller) data model just for this example, don't assume it's better than what you already have (I'm still learning as well!)

I have the TournamentPlayers relation entity and we can select which players will play that tournament:

Let's use the Sixth Tournament that has all 4 players in it:

From the Tournament List we can go directly to a screen to add Round 1 scores to all players:

Important note: After setting the players and "starting" the tournament, we can create the HCP and Round1 (2, 3...5) relations with empty values. So we would see something like this:

Maybe the date or other inputs would be the same for all (not sure about how each round is played), but you can see we could fill each player's Round 1 details for this specific Tournament. We would have different screens for Round 2, 3...5. Again, there could be a better approach for 'n' rounds. But let's leave it for now...
For Round 1 inputs, we could have a screen with this Aggregate:
Since in this screen we only want data for Round 1, we need to assure that in the join:

Then we can have a list of form's:

The container below the list can be 4 col's width and have some padding. Also use "overflow: auto;" in the list widget if you can't see more items or scroll in the screen.
The save action will need to cycle through that list to Create Or Update HCP and Rounds. Just remember not to do it in Client actions since it will call several server actions (group them all in a single server action).

After saving some random values, we should see them in the Hcp List screen:

And in the Round List screen:

Please let me know if this helped you in any way!
Thanks,
Fábio