Background:
last sunday(9/17), my father suddenly felt a numbness on the right side of his body - his mouth felt a kind of "pull", and though he did not lose mobility, he found it difficult to sign. My mother immediately gave him an aspirin and took him to a doctor, who diagonized it as tia. However, the symptoms did not completely disappear in 24hrs (which I believe happens with a tia).
It is now almost 10 days since. The 'pull' in his mouth is almost gone, but he still has difficulty signing - cant sign more than twice continuously. He was able to drive, two days after, though he avoids it as far as possible.

He met a neurosurgeon the next day who advised him to undergo a suite of tests. Here are some of the results.

Test results:
ecg: aortic valve sclerotic
homocysteine: 65 (recommended <13)
ct scan: focal low attenuation in the left thalamus. Also shows a small dot in his brain, which the doctor refered to as 'scar'. This, according to the doctor, is in a place that controls motory actions, and so the difficulty signing.
Mri: my father felt an excruciating pain in his neck when he was strapped, and also felt claustrophobic, so refused to take an mri.
Doppler test: nothing unusual

lifestyle & history
my father does not smoke or drink and is a vegetarian. He is 58 and has had high blood pressure for the last 20 years or so,controlled by medicaiton. Diet is fairly balanced. He smoked for about 5-6 yrs but stopped about 30 yrs back. Works in a desk job, and doesn't exercise much. He drinks about 5-8 cups (150ml each) of coffee a day. He had a similar numbness on the right side about 10 yrs back, but tests then did not show anything.

Doctor's diagnosis:
according to the neuro-surgeon, the high level of homocysteine was the cause of a very minor stroke. He has prescribed vitamin b and folic acid tablets, and plagril (a pill containing aspirin) for life.

My questions:
is the diagnonsis conclusive enough? From what I read on the net, it is not clear whether high levels of homocysteine is a cause or a symptom or a fall out of a stroke!
What is the risk of another stroke? The doctor says it won't happen since he's now on aspirin for life.
He has frequent ulcers in his mouth, especially when he eats out. Is it ok for him to be on aspirin?
What is the risk of any heart/other ailment, given this information or background?
He has now started walking 30 min a day and is trying to cut down on coffee. Is this good/sufficient?
Are there any other tests he should undergo, which might reveal more?
Is it ok for him to start driving so soon?
Appreciate your advise!