It might help with recognizing the kana, if you learn to write them, but it’s not a necessity, per se. You could just as well type out the answers if you want, or write them in romaji. If one of your goals is to one day become a proficient handwriter, by all means, practice writing them over and over, just like you practiced your alphabet when you were six.
Minna no Nihongo I really like for grammar, but if you only have the main textbook, the exercises are pretty much only ‘fill in the blanks, with the right conjugation’ for renshu B. What my Japanese teacher does (and what I’ve done during self study as well, at times), is provide a translation of the finished sentence, and then expected up to translate it back to Japanese, using the required grammar. This works really well to get you making your own sentences. For self study, it first requires a good understanding of the grammar, of course. So you could one day work on understanding the grammar on one level, translate the sentences in the book. Then a few days to a week later, try to translate your own sentences back to Japanese. See if you come up with something close to what the book initially said. You can maybe use the days between to study the vocab list for that chapter, so you don’t have to look up as many words when you translate back to Japanese.
For this I’d like to recommend katsu. With this webapp, made by a guy in my language school, you can practice making certain conjugations, depending on what you toggle, and you can also practice recognizing the conjugations if you choose to reverse the exercise, so you get a conjugated form, and you have to answer with the base verb/adjective.
WK level only tells you how many kanji you might be able to recognize. Grammar is a whole separate beast. Seeing as for now building kanji doesn’t seem to be an immediate concern for you, why not take a break from WK and only do reviews for now, and try to put more time into grammar? You can use various threads here to help you with it, for example the Japanese Sentence a Day Challenge.
Don’t try to go too fast through the grammar. I don’t know what your pace has been, but basic grammar is important to get lots of practice with. On the other hand, don’t get too bogged down by details and exceptions and classical origins for now.
Good luck!