Further the percentage loaded on each ship does not follow the percentages shown.
The loadout determines how the fleet will spend its transport capacity, not how each individual ship will.
From the fleet screen how can I tell the load size of a particular troop. All I can see is a percentage which means very little to me unless I can see the troop load size.
You can calculate it out from the numbers of troops listed next to the percentages, or you can remember that infantry and special forces each use 100 transport capacity, armor uses 200, and planetary defense units use 400. If you do try to calculate out the unit sizes from the numbers given, be aware that whatever computes the number of troops appears to think that special forces are twice the size that they actually are (hence why you see only 3 special forces listed in your fleet loadout; it's either that, some kind of rounding issue, or an accounting error while trying to check how many troops can actually fit into the remaining space on the fleet's ships).
Note that the entire unit must be present on a single transport ship, which means that transports with capacities which are not integer multiples of 100 are somewhat unhelpful - for example, in your fleet you have 4 transports each providing 640 transport capacity, which gives your fleet a nominal capacity of 2560. However, 160 of this capacity is unusable due to it being in 4 chunks of 40 capacity, meaning that your fleet can only carry 24 units of infantry instead of the 25 indicated by its nominal capacity.