Yes if your bf staying at your place you will need to go to immigration with him within 24hrs to register him or your father faces the fine. Apparently some condo managements know about this so worth speaking to you condo management as they may be able to do for you and save the hassle

Correct only if you go to local immigration for extention you are likely to get fined now

Samwise Fila this was my 3rd extention this year and 1st fine.my mate did it last week no fine.the guy in front of me was renting and got told agent liable for fine.its up to property owner to let immigration know of tenants movements

If you rent you have to take copy of rental contract if you own you take chanoot or if don't have chanoot take contract of property purchase

I got fined 1600 baht this week when doing 30 day tourist visa extention. As property owner I've to go to immigration now within 24hrs of arrival back into Thailand.I or face 200 baht daily fine. I now have aTM30 in my passport to show immigration on my arrival. I can't see a problem you leaving as not overstayed however things are changing so . I was told it's the owner of property liable for fines and for letting immigration know of tenants movements and the tenant has to also go down within 24hrs of arrival with passport and get TM30 card. Maybe when you go Monday you can explain but expect a fine

Yes overstay payment at airport an option as I've done this myself for 3 days so cheaper than 1900 baht.however 18 months later on entry with same passport I got pulled aside by immigration and asked to explain my overstay