Kindly ask your cousin to get scaling and polishing done and if he wants he can even get bleaching done. He should brush his teeth twice daily using correct brushing technique to maintain his oral hygiene. The cost of the treatment depends on various factors like dentist to dentist it may vary.
See as you must be already knowing, any medicine intake should be avoided in first 3 months of pregnancy as it can have harmful effects on baby. So, try avoid taking any medicine. What you can do is do "Cold fomentation" that is keep ice at the site of erupting tooth intermittently. Once tooth erupts completely, you will have relief in your pain.
Kindly get the wisdom tooth extracted/removed.
If the molar in front of the wisdom tooth has caries then kindly get the caries removed and get the cavity filled. If the caries are involving pulp which can be seen in the X-ray then kindly get root canal treatment done followed by a cap/crown.
Brush your teeth twice daily using correct brushing technique to maintain your oral hygiene.
Bad breath can be due to many reasons. If your teeth show a yellow or black line near gums, then you might need professional cleaning to resolve your bad breath problem. Bad breath can also be caused due to improper tongue cleaning or decreased water intake daily. I suggest you visit your dentist once for a proper diagnosis of your problem.
Yes it seems you have tobacco chewing habbit. One finger mouth opening is dangerous condition, may be because of fibrous band formed in your oral mucosa stop the habit, take multivitamin antioxident for atleast 1 month, takr S M fibro for one month & contact your local dentist.