I'm gobsmacked at the comments. Wow. Only person speaking any sense is @Vitaminsss.
There is a world of difference between someone who was feckless and failed their family in the past but has now genuinely reformed, and someone who is abusive and controlling. OP hasn’t given any suggestion that her father falls in the latter category.
Neglect is a form of abuse. He has been an abusive father. This man was an addict who was in and out of his child's life and did not provide adequate care. He then completely opted out when she was 11 and is only now, when she's an adult, making attempts to build a relationship. A relationship that OP feels is so insecure that it would be negatively impacted if she decided to return any of the excessive gifts. He's no prince, and whilst he may be "reformed" that is certainly not proven by anything in the OP and it does not undo the extensive damage he has already caused.
OP, it will have given him great pleasure and comfort to feel that he can make these gestures to you and the kindest thing that you can do is to let him have that
WTF am I reading. This is literally the whole point! A gift should be something nice you do for the recipient. This is not a healthy gift, where it's all about his pleasure and easing his guilt and shame, regardless of how it actually makes OP feel (pretty shit, it would appear). And where she feels that letting him know that she feels bad would result in some negative impact on the relationship. He's not doing it for her, he's doing it for himself. OP - like any victim of parental abuse, past or present - has no obligation to accept unwanted gifts/communications etc in order to assist their parent in appeasing their own guilt. She doesn't need to be "kind" FFS. Think about what you're actually saying.
FFS, he's not an acquaintance, he's her bloody dad!
Not in any meaningful way he isn't. He wasn't there and didn't provide for her physically, emotionally or financially. She owes him nothing at all and it's very wrong and very harmful to promote this idea that a person is entitled to any form of intimacy, relationship, trust etc simply because they are a biological parent, without any actual parenting having gone on. How is he entitled to any of this, any more than anyone else she recently met would be? Why do you think there's such a huge distinction between him ("he's her bloody dad!") and anyone else?
I don't think some posters here understand the sense of obligation that a child can feel in these kind of circumstances and how harmful that can be. There's certainly not much in the way of nuanced responses.