Suddenly, at 37, I have allergy induced asthma. I was prescribed ProAir. I take Toprol 50mgs for HBP & SVT. I'm afraid to use the inhaler. Any advice?

Ideas. Have you gained any weight over the last several months? Since you have hypertension and SVT, it does make me wonder about sleep apnea being significant. In any event, if you are overweight, it would make me wonder about gastroesophageal reflux which could present as cough or asthma. It is felt that as many as 50% of cases of adult-onset asthma are tied to reflux.
Get off the Beta- Blocker (Toprol ). Beta-Blockers make asthma worse & harder to treat. Do this in concert with your physician. You will likely need to be given a substitute HBP Med , from a different class, that doesn't effect asthma,in order to maintain good HTN control.Even though it is a "Selective" bb, u may b reacting to it.
Use the inhaler. Do not be afraid. Your beta blocker, metoprolol {toprol], may aggravate asthma and interfere with albuterol. . Experience will determine how much it helps slow the rate of SVT and how much it is a problem with asthma. ABLATION is the way to go for SVT. As you get older SVT will get worse, so you will eventually get it anyway. It is a cure. For asthma you MUST avoid smoke and stay far away from cat.