Thanks for playing!
I've been getting a lot of camera comments (both here and in the threads) so I think experimenting with it will be a big priority going forward.
In terms of attacking, I think the source of your confusion is that a diagonal counts as 2 spaces. So units with 2 or 1-2 range weapons (bows or tomes) can only attack at the diagonals that share a corner with the tile the enemy is on. When you're in the screen where you select an attack target there should be an outline showing the unit's attack radius.
Counterattacks occur if the defending unit can attack at the range your attacking from, so if you attack a bow from 2 range with a tome they can counter but if you attack them at 1 range they can't.
Follow up attacks, occur when you're attack speed is 5 or more higher than your opponent's. Attack speed is a combination of a unit's speed and encumbrance penalties incurred by using a weapon higher than the unit's constitution stat. This part would've been more obvious if you had a chance to look at the stat screen, but since you were playing on laptop you weren't able to do that.
These interactions are lifted 1:1 from Fire Emblem so I'm likely not going to change them drastically but I'll see what I can do to make it more obvious to players.