You can't ride bicycles on interstates, were you aware? It's the (fed) law. The fuzz will arrest your sweaty mug.
......
I also heavily agree: get rid of them knobbies for pavement riding, get smoother tires. Knobbies squirm and waste a lot of pedalling energy on pavement. Get the correct-width innertubes for the narrower tires also.
-----
33 miles is not long, most average people can manage 12 MPH over flat pavement without a lot of effort for at least a couple hours. ....Are you just riding one-way? Or out and back? ....What will kill you is headwinds if there are any--if you are going one-way, hope that the winds are at your back.
PS. your bicycle sucks. Your ass is gonna hurt you bad amigo. If you desire to do long bicycle rides in comfort, get a recumbent. CLWB's are generally easiest for beginners to ride.
Two lower-priced brands are
Sun and
Cycle Genius. If you wuss out of being a 'bent-wierdo then you can cough up the money for a
Rans crank-forward bike -- it looks like a mostly-normal bike, just sits a bit lower but is still drastically more comfortable,
especially over longer distances.
Riding long distances over flat ground really isn't difficult; the "pedalling" is actually only a small part of the effort involved.
The reason most adults don't like riding
conventional bicycles is because a regular bike makes their butt, back, hands and neck hurt. Those parts of your body hurt long before your legs really get tired.
Recumbents have common rider pain attributed to them, but it is not as severe and it takes
much longer to occur during riding. The pain you get from a recumbent is pain in your LEG joints, from pedalling so long--like four or fives times longer than you would ride on an upright bike.
~~~~~