As the title says, could this feat just be turned to half feats and would that break balance too much

Artificer initiate;
This feat is closest to Magic initiate with difference that you get one tool proficiency instead of one cantrip. I could hardly call that an improvement.
And Magic initiate is not one of the strongest PHB feats, and it gives more options in what spell lists you can chose. This one is locked to one list.
Maybe if it provides expertise to one tool in addition and/or spell is recharged on short rest it would be worth a full feat...maybe.

Eldritch adept:
this is the feat that most looks and feel like a full feat. some invocations are really good, but they are locked to warlock class so that does diminish the worth of the feat, not to mention as you get more invocations "good" choices for your character concept are running out.
maybe make it half-feat and limit to only invocations that require no warlock level(that is what you can take as 2nd level warlock).

Fighting initiate:
This is plain half feat.
Almost in every single situation +2 to your attack ability is clearly better than a fighting style. By a lot.
And there is no sense in having this feat as a secondary option at 12th level when your attack stat is already maxed and 90% of campaigns are over.

Metamagic adept:
this would work as a full feat if it gives more sorcery points, maybe equal to your proficiency bonus or/and add 3rd metamagic option at 11th level or similar.

or just 1 metamagic option and 2 sorcery points for a half feat.

Poisoner:
lots of little benefits that in the end do not add to a lot.
poison DC should scale with your proficiency bonus. maybe 12+PB,
number of doses equal to twice your PB.
add non costly option for poisons that last only 24hrs and deal less damage. I.E. 2d6. So you cannot stock on them. make it that production is a part of the long rest.
damage could also scale:
1d8 for costly poison, 1d6 for free one
2d8/2d6 at level 5,
3d8/3d6 at level 11,
4d8/4d6 at level 17,
or just take the printed version, reduce the damage to 2d6 and make it half feat.

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