Uses of 'after all', 'withal', 'anyway', 'anyhow' instead of 'however'?

Whether any of the words you suggest are apt alternatives to however depends on the sentence--its intended meaning, its syntax, and other stylistic choices.

Although we could multiply examples of how your alternatives to however could or could not work in a given sentence, perhaps a few representative sentences might clarify this issue.

My doctor thought I should have the surgery. I, however, had a different idea.

• I, after all, had a different idea.

• I, withal, had a different idea.

• I, anyway, had a different idea.

• I, anyhow, had a different idea.

Clearly, none of your alternatives seems to work in the above sentences. They could be made apt, but the intended meaning of the sentence would need to change. For example,

My doctor thought I should have the surgery. I felt differently. After all, I too am a doctor.

Here is, I suggest, an apt alternative to however:

My doctor thought I should have the surgery. I, on the other hand, had a different idea.

Or to provide better parallelism, you could word the sentences as follows:

On the one hand, my doctor thought I should have the surgery. I, on the other hand, had a different idea.

In short, the substitution of one word for another depends largely on the semantics of the sentence(s). Furthermore, I suggest your substitutes are of a different sort, semantically, than however.

“Anyway” will change the tone, but you can use it in the end. As in “recommended to hire anyway”.

“Anyhow” means the same as anyway, but is informal.

“After all” usually indicates there were serious doubts. It is usable here but seems out of place. If it went like “he has a felony conviction and smells bad”, then “after all” would be justified.

If you want a viable alternative to “however” you could use “still” or “nonetheless”, or begin the sentence with “and yet.”

I cannot comment on “withal”. It is probably so archaic that I’ve never heard it.

Also. “Recommended to hire him”, not “him to hire”. Or him to be hired.