I am trying to create a feat that I can use to represent the broad knowledge and experience long-lived races should have after living for decades, and sometimes centuries. 

The Bardic Jack of All Trades would be perfect for this, but I would like to make this class feature a general feat so that characters don't have to dip into two levels of bard to simply add half their proficiency to skills in the same manner as the Bard's feature.

However, when I tried to create this homebrew feat I ran into two interesting limitations.

1. I can give half proficiency across the board for all abilities, but that means that proficient skills get the bonus as well, which is too overpowered to my mind.

2. You can choose either a 'half proficiency' or a 'half proficiency rounded up' when creating a feat but they both seem to result in the same boost (half rounded up), which is not the same boost as what the Bardic feature gives, which is what I want. 

Any help would be greatly appreciated and I would like to make this feat publicly available when I have all the bugs worked out.

I tested this. I made a feat, added modifier Half Proficiency, subtype Ability Checks, left everything else unedited. Saved.

Added to character. It works precisely like the bard feature. Skills I have prof in remain the same, skills and Init get half prof added. It's 100% perfect copy of the bard feature.

So, I'm guessing you have something else on the character, not applying the math right or messed up when adding the modifier.

Thanks. Could be true, it was an afterthought for an established character. And now that I know it works I can keep noodling until I can get it to work.

Yep. Works fine now. The character I was testing it on had other features that were affecting the calculation. 

I have also made it public as I promised.