Moreover, a solid navy suit, or a solid medium grey suit, needn't be so overly formal as you seem to suggest. Worn with the right shirt, tie, and accessories, it can definitely be far less "serious" than with other pairings. The solid navy which is a "power suit" when worn with a white point collared dress shirt, burgundy silk necktie, and AE Park Avenues, can be downright friendly when worn instead with a pink OCBD, madras bow tie, and penny loafers.
(I would also ask whether your plans to be a professor are likely to be realized in 10 weeks, or in 10 years. Timing matters, and buying clothes for current and near term needs, rather than needs which may materialize at some unknown time years down the road, is often the wiser course. But that's perhaps more of a side issue.)
But assuming you will be a professor in the near future, and you choose to dress relatively informally (academic business casual, if you will), you could probably get by with a "work wardrobe" consisting largely of chinos, a couple of pairs of cords (for the cold weather, assuming you're someplace that experiences winter), some OCBD's, and maybe a few sweaters. If an occasional sport coat is desired, some inexpensive lightweight thing (warm weather) and one in tweed (cooler weather), would cover those needs.
Still no real argument for a less than optimally versatile plaid suit (which, again, I rather like - so long as you've already taken care of those "maximum versatility" suits constituting the core of your suit wardrobe), and especially no argument for the weird green jacket.