Sounds like an adventure, though I have no clue where I'd start.
Although I find a number of... 'strange' things on the site, perhaps the
League of Michigan Bicyclists might be a starting point. Their advocacy for cycling (even in its stranger forms!) looks commendable, and similar(ish) to the Cyclists' Touring Club, here in the UK (national cycle advocacy group - they changed from the term 'bicyclists' in 1883, however, to not show discrimination against other configurations of machine...
).
I saw a few places named under a Michigan Cycle Club search (Royal Oak is 90 miles away, unfortunately, and Lansing only slightly nearer according to the usual on-line tools) but perhaps a search of your own would be better, given that I don't know your area/state well enough to understand either its geography or its communities.
(Not saying you should run off and immediately join a club or other organisation, just perhaps keep an eye on the calendars (apparently May is the month for cycling advocacy) and other announcements. And if a Slow Roll (not, as I feared, a disruptive protest, but a casual 'pootle' suitable for all ages and abilities of cyclist) is organised within easy getting-to distance of you..? Might be worth a look, right?)
Getting your milage up would be good. Going round in circles, for multiple laps isn't exactly rivetting, but at least you're always near your base of operations. (OTOH, it's also easier to give up when passing by for the umpteenth time, when you
were planning on doing half a dozen more circuits but are feeling a bit sore.) I really don't know if I want to send you on long-looking journeys on the open road, alone, but it
can be rewarding to do them, so if you do find some friendly club-run or other that you can tag along with.
Don't worry too much about hitting that 30mph you mentioned earlier. Even 21mph is more 'racing speed', and perhaps 12-15mph sustained (on the flat) for 10 miles (perhaps by circuits of your par for half an hour) , 20 miles (using out-and-backs on routes radial to your starting point on friendly-looking roads, for a couple of hours including a lunch-break) and upwards, and building up that way would be a suitable aim to get you to a group-riding level of capabity. Talk this through with anyone you're prospectively joining, though. You don't want to find youself joining a 90-mile 'burn up' training session or attempting half of the Race Across America, too soon.
Build up endurance, first, even if it means 'windmilling' in a low gear for very little forward speed, when you'vre getting tired. Pushing the big gears for short periods isn't something you should overdo at the start, but you could perhaps set up a beeper on your watch/phone/cyclecomputer to prompt you to do maybe a minute of power-training and then four minutes of a more sustainable speed without straining yourself, repeated for the hour, two hours or more that you can stand to keep it up.
Meant to comment on the bike, but forgot. Looks Ok, and Ivve seen far less 'road capable' machines in use. Remember to lock off that suspension for normal road riding (so long as it isn't rutted dirt-road, anyway!) as it tends to soak up pure forward effort as much as minor irregularities in the road surface, so you have to balance the two demands. Or perhaps exploit this effect for your endurance-training?