Dog Won't Settle When Away From Home

I have a male 3y/o chi/terrier mix (we don't know what kind of terrier specifically). He's neutered. He was crate trained until he was about a year old.. this is important for later.

He has a really hard time settling when we're anywhere other than at our house. We stayed for a week at my boyfriend's house and he was pretty okay.. he'd have trouble settling initially when we first got home from work, but after about an hour of whining or taking his "girlfriend" (a fluffy pink pillow) on a "date" (I feel like you can catch my drift) he would settle.

Whenever I take him anywhere else to, like, my best friend's house, however, he does not settle. He's a whiner - he will whine and whine and whine forever. I strongly believe that this is because he's become so attached to my mom. My dog and I have lived with my mom since I first got him when he was 12 weeks old. I work and until recently was in school, but my mom worked from home for 2 years and has been retired for a year. My mom's also far more of an introvert than I am, and doesn't go out much to socialize. Being retired and introverted, she's home 99.9% of the time - whereas I'm home maybe 70% of the time between my commitments.

The problem is that she never wanted to be involved in any training. I crate trained him (which promptly stopped when my school went back in-person), I trained him to sit/lie down/paw/wait,etc., I potty trained him, I took him to puppy classes, I took him on training walks, etc. Now I'm not complaining about any of this - he's my dog and my responsibility, 1000%. What I don't think I took into account is how attached he'd get to her and how much her not engaging in training would regress the training that I do.

Now that plus the fact that she's introverted and doesn't like people over at the house (as an example, my boyfriend of over a year - that she has met, and likes very much - has never been inside our house) means that working on training him around other people in a familiar environment is not an option.

So.. I'm just wondering what my options are here. I'm a fairly social person and would love to be able to bring him with me more places. Is "weed" (or whatever the dog equivalent is) a good option? Am I screwed until we can move out and I can make the training/trained behaviours his norm? Is there another option that I'm not seeing?

Sorry if this isn't coherent - I'm writing all of this very tired and at the end of a long day, lol.

TL;DR: my dog cannot settle at other peoples' houses, I'm not able to train him in a familiar environment, and I feel very stuck.