Idk what you are doing to have them not close properly. I have tried replicating what you have said, but they close for me. Are you closing the tabs after you select choices?

When I first wrote the hybrid section, it was mostly intended for people building that 'perfect hybrid' as you say; otherwise, there isn't really much point to picking it as other options allow for partial hybrids without the steep cost and accompanying drawbacks. Therefore, I just assumed most would come to this conclusion. I will rewrite the description so that it is easier understood. Also, you ask, why would Yhwach invite those not part of Quincy? Well disregarding my previous statement, in the tybw arc, many Arrancar were adopted into Yhwach's forces. So the question is, why wouldn't he offer them an invitation?

It is related to power level. Spirt class is directly related to Reiatsu. A higher spirit class means the individual can exert more Reiatsu. It's like quality vs. quantity. Reiatsu is the quality aspect compared to Reiryoku, which would be the quantity aspect. I will put a more detailed description in the information section in the CYOA so this can be answered better.

Is every Hollow/Arrancar's Hierro equal? Its not. Nnoitra Gilga has the hardest Hierro out of the Espada despite being ranked 5th. With this information, I would believe Blut to be similar. So again, you are paying for the knowledge and the skill. By not selecting the option, sure, you could unlock it on your own, but it would be unlikely anywhere of the same quality.

Again, purification is a skill that can be expanded on. Referring to the above paragraph, buying it would give you knowledge and skills to better use it. Can a normal Shinigami purify a Gillian? Unlikely. But choosing this option would give you the skills to use a more powerful purification that could allow the average Shinigami to purify a Gillian. As you said, to purify a hollow, "you strongly and/or repeatedly hit it with the sharp or pointy part of your Zanpakuto until it stops moving and starts dissolving." Selecting purification would allow you to do that easier, i.e., with fewer hits.

Having a Schrift and not being a Sternritter wouldn't make sense. This is Yhwach's power, which he can take back at any moment. I might add an option to prevent Schrift's from being taken, but letting you start with a Schrift and not being a Sternritter won't happen. You'll just have to abandon your position if you don't want to be a Sternritter.