Not hyao here but I can answer a couple of these!
With bernard no you can do much more than just the love potion it just requires certain parts of the his and Logan's storyline being done, specifically the area you choose him or logan to save which depending on who you pick will give you a heart with them! And if that's done bernard has other things to raise his hearts which since you have two I'm assuming you have already done the date at the bar, the hangout at the hut and maybe the his invite to the bathhouse. The bathhouse invite is after a you have slept with him in the same bed at the hut and he has 2 hearts I'm pretty sure so this could be your thing, meaning you just gotta sleep with him. But also it could be you just gotta visit after dark for an evening at his place. Try that one first cause it's less effort.
The bug issue's you can report here in the comments where he should be notified of them.
For Harold I'm unsure and is why I said I can say a couple.