For tachycardia I recommend combining coleus forksohlii with watercress or nettle leaf. This will slow the heart and strengthen the contractions. It will also dilate the bronchioles to help increase O₂ levels. the watercress, which works the best, or the nettle leaf will prolong the effects.

I also recommend the herb suma, which helps support the adrenal glands, which prevents over release of epinephrine from the adrenals and also helps with oxygen utilization by the cells.

For the gas I recommend yucca root, which is a natural surfactant. This reduces the surface tension of the moisture in the digestive system allowing the gas to go in to the solution.

ALS is believed to be triggered by a virus. So there I highly recommend the antivirals chaparral, andrographis and pau d' arco combined.

ALS is also classified as an autoimmune condition. Autoimmune conditions are frequently triggered by microbes, but also result from adrenal dysfunction that leads to the overproduction of low affinity (nonspecific) antibodies due to decreased levels of immune modulating corticosteroids. Therefore I also highly recommend building up his adrenals:

http://curezone.com/forums/fm.asp?i=1527351#i

All the herbs are best taken 3 to 4 times daily at least 20 minutes before meals.

Either your dad's doctors didn't do an EKG (which just doesn't sound right) or they did and they're not giving him all the information.  A rapid heartbeat in that range is very often associated with atrial fibrillation.

http://www.emedicinehealth.com/atrial_fibrillation/article_em.htm

• Instead of a coordinated contraction, the atrial contractions are irregular, disorganized, chaotic, and very rapid. The atria may contract at a rate of 400-600 per minute.
  
  
• These irregular impulses reach the AV node in rapid succession, but not all of them make it past the AV node. Therefore, the ventricles beat slower, often at rates of 110-180 beats per minute in an irregular rhythm.
  
  
• The resulting rapid, irregular heartbeat causes an irregular pulse and sometimes a sensation of fluttering in the chest.

I've had 175 BPM during atrial fibrillation - it's common.  I learned a couple of things and was able to cure my afib.  First I learned through listening to my body (I could eventually tell when I was in afib) that it occurred after drinking coffee or any other caffeinated beverage - including tea.  Secondly, I learned that I have Type II diabetes and that eating a lot of carbohydrates would get me into afib.  Also a low-carb diet is recommended by Dr. Weil to lower blood pressure which is what the beta-blocker (ugh) Bystolic is prescribed to do.

http://www.drweilblog.com/home/2010/4/12/lower-carbs-and-blood-pressure.html

Regarding the CO2 - that's a symptom of improper breathing - breathing too rapidly.  The elevated CO2 is also a leading cause of hypertension.  Learning proper breathing can do a lot to lower CO2 and reduce BP.  I've found that the 4-7-8 breathing exercise, also recommended by Dr. Weil, can lower my blood pressure almost immediately.

http://www.drweil.com/drw/u/ART00521/three-breathing-exercises.html

Vitamin D deficiency is common in everyone and is a recommended supplement for ALS.  This site recommends 2-3000 IUs per day, but I've seen much higher recommendations for those who are deficient.

http://www.purehealthmd.com/conditions/neurological/als/als.html

Best to you in helping your dad.