▲碰巧查到你的两个句子均出自张道真与温志达合编的《英语语法大全》的“插入语”一节。你问句中若有实意动词、情态动词或者有助动词等，插入语的位置问题应如何安排，其实插入语的位置是比较灵活的，比如下面的句子均出自《英语语法大全》：
The boy, I think, has come from the country.（插入语放在助动词 has 之前）
His manners, it is true, are awkward and silly.（插入语放在系动词 are 之前）
That gentleman, mark you, is the big boss of a big firm.（插入语放在系动词 are 之前）
His wife, I presume, was not listening.（插入语放在助动词 was 之前）
This house, I know, will be sold to a rich man.（插入语放在助动词 will 之前）
A very beautiful fairy, so the legend runs, has appeared here.（插入语放在助动词 has 之前）
What we have done is, on the whole, satisfactory.（插入语放在系动词 is 之后）
They are mostly, remember, robbers and pickpockets.（插入语放在系动词 are 之后）
He has, oddly enough, married eleven times and yet has not a single wife.（插入语放在助动词 has 之后）
▲另外一个位置比较灵活的典型插入语是 howver。如：
Later, however, he changed his mind. 可是他后来改变了主意。（放在主语之前）
He hasn’t arrived. He may, however, come later. 他还没有到，不过他等会儿可能会来。（放在情态动词 may 之后）
He said that it was so; he was mistaken, however. 他说情况如此，可是他错了。（放在句末）
However, not everybody agreed. 然而并不是人人都同意。（放在句首）
My father, however, did not agree. 但是，我父亲不同意。（放在助动词 did 之前）
My room is small; however, it’s comfortable. 我的房间很小，但却很舒服。 （放在分句句首）
Sales, however, were little changed. 但销售额变化不大。（放在助动词 were 之前）
She waited, however, for no explanation. 但她没有等候解释。（放在动词 waited 之后）
Christine, however, was enjoying herself thoroughly. 而克里斯廷却玩得很尽兴。（放在助动词 was 之前）
He went through all this. He was different, however, from the others. 他经历了这一切，但他却与别人不同。（放在系表结构 was different 之后）
I’ll offer it to Tom. However, he may not want it. 我将提出把这个给汤姆，然而他可能不要它。（放在句首）
▲从以上实例可以看，插入语在句中的位置是比较灵活的，到底放在哪个位置，与说话者（写作者）的态度有关：一般说来，放在句首或句末会比较强调，若放在句中则显得没有那么强调；另外有时也会将插入语放在与它关系最深的词附近。比如下面两句，however 都是放在系动词 be 之后，但一个放在 not 之后，一个放在 not 之前：
She was not, however, aware of the circumstances. 但她对对并不清楚。
He was, however, not a hundred percent convinced. 但他还不是百分之百相信。
第二句将 however 放在 not 之前，多少有强调 not 之意。